Disclaimer: The following fanfic doesn't follow Dragon Ball Super Canon, it follows Dragon Ball Multiverse one. In the same way, unlike Kanassans, I cannot see the future, so don't expect me to follow the DBM canon established after page 1441 either. In short: No Beerus, no SSG, no Golden Form.
Freeza's ship was landing on earth, at distance, Gohan, Piccolo, Vegeta, Yamcha, Bulma, Krillin, Tien, Puar, and Chaos were observing, lowering their ki to pass undetected to the soldiers scouters. They could feel two overwhelming powers inside. One of the two was recognized by Vegeta, Krillin, Piccolo, and Gohan. It was clearly Freezer's; the other one was unknown to them but similar to the former, if not greater and darker.
"This is him," said Gohan with a serious look "No doubt about that, Freezer is still alive"
"There is more than that," said Krillin worried "There is someone with him, is even more powerful"
Piccolo nodded, then Yamcha spoke up his mind "Let's get this straight... we are nothing more than bugs to them, how we are supposed to fight them?" then the namekian answered "Can you stop crying? Go home if you are here only to complain. But I believe I have a plan, just let's wait a bit"
"Is that so namekian?" smirked Vegeta "This backwater planet is doomed, you better get to the idea"
Piccolo was indeed lying, he was internally as scared as Yamcha if not more, but whimpering around was not going to help. Maybe he would think on something later. And maybe even Yamcha would be a piece of a brilliant plan... hopefully one that doesn't involve any saibamen.
The spaceship opens its gate and Freezer and its father, King Cold, fled outside, followed by a platoon of low-level soldiers. Freezer was different from the last time Gohan saw him, almost all covered in scrap pieces, the father reminded him of the tyrant second form. He was wearing a black armor, not much different than the rest of the imperial soldiers wore, but with a long black cape on his shoulders.
"So..." said Freezer observing the environment "This is Earth, nice planet, we could make a nice profit after killing its inhabitants"
"We are not here for planet trade, son," said King Cold with a serious frown "We are here to kill that so-called Super Saiyan. We are here to make an example to anyone in the universe who dares to stand up to us"
"Indeed, dad, with you at my side and me being stronger than before, he should be no problem" he frowns, remembering the humiliation he suffered at the hands of the dirty monkey "But first, we should make him suffer, for example, killing the ones he loves" the tyrant looked at the soldiers "You, start the search, and kill any earthling you find... I wonder how many you can kill in three hours"
As the soldiers departed, Freeza was laughing a lot, like a maniac. Piccolo looked at Tien, Chaos, and Yamcha "You should stop them and bring Bulma to safety while we wait here" all of them nodded while Krillin speaks up "Wait? And me?" Piccolo frowned "Maybe we will need your kienzan"
When the three warriors departed with stealth someone else arrived at the field, the two frost demons were as surprised as the earthlings were. A third frost demon walked slowly towards the other two, he was similar to Freezer, but purple in color, and had a bio-helmet around his head, as well as other parts of the body, but it wasn't obvious if they were bone-plates or actually part of the armor he wore, one similar to the one King Cold was wearing, but with a single pauldron and a red cape instead of black. His body was full of already healed scars.
"His ki is also very powerful" commented Piccolo "And despite being not as dark as Freezer, it seems cruel and vicious..."
"I know him" commented Vegeta "He is Cooler, Freezer's older brother... I have never seen before, but it must be him"
"We are doomed, three of them!" complained Krillin
"But wait..." said Gohan "The symbol on the pauldron, it is a Capsule Corp logo?"
"What?" exclaimed Vegeta "How it can be possible? What dealing have do you maggots with someone like him? The loud-mouthed woman works for him?"
"We have never seen him before," said Krillin scared of Vegeta "There must be some explanation, maybe someone on Cooler's army has a symbol similar to Bulma's?"
"Yeah... that should be it," says Gohan
"Silence!" said Piccolo "They could hear us"
"Oh, brother," said Freezer "What a surprise... what the hell happened to you? And more importantly, how do you know we were here? Dad told you?"
"I didn't tell him," said Cold "It's not like we needed to either, we are just going to kill a monkey. What I'm wondering is, why are you wearing the imperial cape? " Cooler didn't answer "It doesn't matter, we will discuss that latter, we need to focus on the super monkey now... Its good that you came here, with the three of us here he will stand no chance"
"Actually" Cooler finally spoke up, staring into his younger brother, the Z-warriors could sense his power level increasing "I'm here to do something I really wanted to do since you were born..."
"I didn't give you two permission to fight, especially not now, we have a super Saiyan to hunt, the one who hurt your brother" said Cold, percieving Coolers menace "As I said, your quarrels..." then he saw the murderous glance his son threw to him "You impudent little brat! How did you dare to look me like that? Are you planning to betray us? I'm going to give you the beating you deserve!"
"Wait, father," said the younger frost demon "Let me discipline him... I was stronger than him before, and now I'm even stronger. He will learn some respect"
"Go on my child," said King Cold "We have three hours if you get too tired ill face the monkey with my first restricted form. You have my permission to kill this traitor"
Freezer smirked and launched a blast to his brother, who dodged and flown upwards. Cooler was followed and they started exchanging blows, Freezer was faster but Cooler efficiently deflected all its attacks avoiding useless movements.
"They are fighting each other" Gohan exclaimed happily "We might actually get saved"
"Well, his ki is not as powerful as Freezer's," said Krillin "And even if he can beat him there is the father"
"Huh!" Vegeta smiled "Anyways, seeing Freezer getting beat up is worth it, and even if the other lizard fails to kill him, at least he will weaken Freezer"
"You are failing to see something," the Piccolo said, looking at the fight
"What do you mean slug? " Vegeta frowned "The situation its a win-win to us right now"
"That's not what I meant," said Piccolo "Cooler's energy is slowly increasing, he can control his energy. That's why we haven't detected him before... he is just playing with him right now"
Cooler smirked and blocked the metallic fist of his sibling with his hand. Then crushed it breaking some fingers and used his free hand to fist Freezer on the stomach. The tyrant groaned in pain as he felt a purple tail coiling around his neck, followed by a barrage of fists to his torso. When Cooler stopped Freezer coughed blood "How? How did you get so strong?" Cooler didn't answer, just smirked and kicked him to the ground.
The wounded frost demon was slowly getting up from the pile of rocks he got under. He looked at the sky and saw his brother, who was staring at him with his arms crossed "Look, while I enjoy putting you in your place" he finally spoke "I'm getting bored, get to your 100% already... if your metal trash parts let you do that. You have one minute, if you are not transformed in that time, I'll kill you without mercy, I'm not going to waste more of my time with that". Cooler licked his own lips, he truly was enjoying the moment.
On the background, Cold frowned, the result was not the expected and he was certain that his current form was not enough to stop his son, so he got behind the spaceship and started transforming. The transformation was truly painful, he wasn't used to it, and was a form too powerful for him to handle... but according to his calculation, was also powerful enough to defeat any of his sons.
After a while, Freezer got really bulky and twice as powerful, also Cooler was raising his ki, but this time, his limit seemed to be lower than Freezer current level. The younger charged at the older with great speed, but the purple with just one step managed to get out on the way, outmaneuver the faster fighter and fire a barrage of ki blasts to the back of the white. Such barrage of blasts raised a lot of dust. After the dust dissipated, there was an angry Freezer with a burnt back. "How dare you!" said him furious taking his brother by the neck. He was too fast for Cooler to react before he fisted his stomach "You truly are an idiot! You were having the upper hand and you let me go to the 100%! You are going to regret it!" he said while he was pummeling him down and breaking his armor. "But that, is far from the biggest mistake you have made today!" Cooler just smirked and before Freezer could react the later was tripped by a purple tail. While he was flat-footed, Cooler hit his jaw with a lot of force, sending him flying several meters away.
Cooler smirked and lowered his guard "Well, well, you are not a total weakling after all. But you are going to be out of juice soon, so you should stop playing around and start taking this seriously". He was obviously taunting him, but Freezer was too angry to realize it and he flew forward with all his speed, trying to punch him. Cooler just ducked down and pointed his first towards his brother's face, using this own momentum against him. The white frost demon felt to the ground on his back, his head plate was all destroyed and several circuits were sparkling, clearly damaged by the strike. "You truly are pathetic when you lose your temper," said Cooler with contempt "Now I realize that this fight has gone too long"
"Indeed," said a voice from behind the spaceship "This fight ends now, I don't know what are you trying to prove, son. I have seen that you are indeed stronger than your brother" was King Cold on his third form similar to Freezer's one, but without stripes in his pinkish skin "But if you believe that this gives you the right to defy me... you are wrong."
Cooler was nervous, he wasn't expecting that. He got carried away with his revenge against his brother that he failed to sense his father increasing energy.
"Now, kneel before me," said the emperor "Ask forgiveness and I might still consider you my son after a harsh punishment"
Cooler looked at his brother and then at his father. He slowly lowered his guard. King Cold smiled, even in the pain that was for him to maintain this form, his son was finally remembering his place. Then Cooler smirked and his body grew in size, covering his forearms with spikes, growing a bigger bio-armor. His head was covered in a crowded helmet with a mouth-mask, his eyes were crimson red. Before Freezer could even comprehend what was happening before him, his brother raised a hand "Excuse me, brother, I have no time to play with you" said before he disintegrated him with a huge ki attack. King Cold could not believe what he was seeing, there was a form beyond the true form. He should have ascended to the true form while he had the chance. A hard fist to his face threw him out of his line of thought and then felt a knee to his stomach. He endured the pain and embraced his son, crushing him with his giant arms. "Not bad son...too bad you have decided to raise your fists against me and kill your brother. Now I'll have to kill you" Cooler groaned in pain, trying to get out of the grip.
"We should help him?" asked Krillin "He doesn't seem to be toying with his family anymore and he seems to be our best card to beat the father before he gets a chance to transform another time"
"Are you a freaking moron?" said Vegeta "You would get killed only by getting close to them, and trust me, Cooler is as bad as him if not more. Have you seen how pointlessly cruel was to his brother? What makes you believe he will be more merciful to you?"
"Pointlessly cruel?" Piccolo looked at him with disbelief "Sounds pretty much like you"
"You want me to freaking murder you, slug?" Vegeta said angrily
"Well, you can try, but you don't seem to want to be seen by them," said Piccolo before standing up "But as I see it, this Cooler guy might be as bad or not as his family, but its the better chance we have"
Piccolo took off his cape and turban and threw them to the ground before charging towards the tyrant, kicking his feet and making him fall, loosening the grip on the other one.
Cooler frowned and just said "Get out of my way" before charging towards his father again. King Cold launched a fist towards his son, who blocked the fist with his forearm and then kicked his father's abdomen. Cooler then grabbed his arm with both hands and connecting hip with hip thrown King Cold over his back, when the older frost demon connected with the ground he raised his arm, with his entire offspring and slammed him into the ground. Then looked at the namekian and prepared to kill him with a single death beam, but was interrupted by his son, who kicked him in the chin. Staggered by a second he grabbed him by the foot and threw him towards Piccolo, sending them both towards a rock.
Vegeta and Gohan appeared behind him and launched respectively a Galick Gun and a Masenko. Despite them giving them all in their attacks, the emperor was not even phased, annoyed he just blasted them both with two ki blasts, making them both fall to the ground. Then he looked to the side and blasted a flying kienzan with his eye lasers. Krillin was now truly afraid, his triumph card failed him and now was going to die a third time. Then a purple flash came out of the rocks and body slammed the emperor, who fall into the ground and was pummeled down by a ferocious Cooler. King Cold kicked him away and flew to the sky, he was in true pain and knew that he would not be able to maintain his form for longer, while Cooler looked too comfortable with an advanced state. He raised his finger, he needed to end the fight quickly.
"Damn you, son, ill make you dust, along with this miserable planet," said before throwing a supernova towards the Earth.
As the last remnants of his artificial armor felt to the ground Cooler stood up to charge a Supernova towards his father. He groaned, his energy was not only lower than his father but this technique was more powerful pointing downwards than upwards. Both giant yellowish orbs clashed as both were fighting. Vegeta fled quickly towards them and helped Cooler "Galick Gun!". "Makkankosappo" that was Piccolo. "Double Masenko" cried Gohan. "Kamehameha" joined Krilin.
The force of Cold supernova was slowly winning the combined attack, and Gohan and Krillin forces were slowly depleting. "Kamehameha" they were surprised to hear Yamcha voice, followed to Chaos "Dodonpa". Tien was the last straw channeling the most powerful Kikoho he could muster towards the giant ball. The eyes of the emperor were full of fear as he saw the huge amount of energy coming towards him.
Tien felt to the ground almost unconscious but alive, Vegeta and Piccolo kneeled down, feeling completely depleted. The rest of the Z-Warriors let their bodies fall as they were totally exhausted. A figure, exhausted, towered over them, Cold was missing an entire harm and was all-scarred, but survived. Cooler raised his finger against him, the emperor was now really scared "Wait, son" he said, "I'm your father, spare me and take your place as the ruler of the empire, I was wrong about you, and Freezer was nothing but a nuisance, you are..." The sentence wasn't finished, as Cooler just killed him with two Death Beams, one to the heart and another one to the brain "I know your tricks, dear father"
Cooler reverted back to his true form and was smiling. He did it, he finally killed them both, this was a truly happy day for him, and only one thing was going to make his day better. He then looked at the sky and took flight, the third person who wanted to kill was about to land.
Power Levels (I have seen this in quite a lot of fics, so I'm doing it. To avoid putting all that zeroes, I place the M to represent "millions").
PTO Soldiers: Varies (Between ~1.000 and ~12.000)
Chaos: 0,02M (~20.000)
Yamcha: 0,04M (~40.000)
Tien: 0,1M (~100.000)
Krillin: 0,07 M (~70.000)
Piccolo: 2,5 M
Vegeta: 3M
Gohan: 1M
Mecha Freezer: 80M
Cooler (Holding back): 70 M
Cooler (Slowly powering up): 100M
King Cold (2d Reduction state): 100M
100% Mecha Freezer: 160M
Cooler (Powered up): 140M
King Cold (1st Reduction state): 300M
Cooler (5th Form): 280 M (x2 increase)
King Cold (Hypothetical True Form): 600M