Explanation: Goku roughly equals Cell in terms of power; story belongs to Toriyama and everything and Toei and whatnot
Cell tensed his muscles. The Super Saiyan, at this rate, was wearing him out. Brief moments of respite seemed to be the only things keeping them both going in the fight...
Being a bioartificial being, Cell lacked the urge to breathe in a labored manner as was custom among inferior beings. Such a small thing, the lack of looking tired, would begin the make the Super Saiyan feel more tired and worried himself...Cell thought. In actuality, Cell had never fought another person so equally before. He was slowly beginning to wear down, but his body was simply not allowed to show it.
Looks like he's not going to make the first move...
Cell flew towards the Saiyan, catching him off-guard with a punch to the cheek. He could feel the vibrations of his jaw weakening passing through his fist, getting ready to shatter in a few more punches. The Saiyan countered with with a punch to Cell's face in mere nanoseconds. Blood stained the arena, first gradually, then rapidly as the two powers began to use their maximum speed in punching and kicking each other in the aie.
Damn! What's he trying to do? Break my jaw? I can't fight like that...
The time to act, Goku decided, was then. Cell had given him one of the best fights of his life so far, but he couldn't have Cell kill him and destroy the world. The only back-up he would have would be Gohan...
Thrusting his fist fowards, Goku let out a battle cry and strained his body beyond full power, his punch penetrating Cell's abdomen and destroying any internal organs the monster might have had in there.
Cell staggered back in the air, almost comically. His clutched the gaping hole in his stomach.
"No... damn you... bastard!" Cell allowed himself to breathe more heavily, needing more oxygen intake to complete the regeneration process. "You're a bit stronger than I thought. You shouldn't have been able to do that, no, not with your power... unless..." Cell paused to take in more oxygen. "Of course. You overexerted your body, putting out much more power than you should have been able to. I saw it for a fleeting moment, your muscles puffing up. If you need to resort than an amateur technique like that..." The regeneration process completed. "Then it appears I am already winning this fight."
"You talk big, Cell. But I ain't the one who got a hole in my stomach." Even in his retort, Goku could not deny the truth in Cell's words. The power that he displayed in a fleeting moment, that was the power he needed to defeat Cell. Not with his current power.
I've got one technique that can do that... that can push me beyond by limits, without puffing up my muscles... but can I even use it in the Super Saiyan state?
Cell resumed the fight, flying towards Goku and throwing a sharp hook to his face. As they exchanged blows, Goku slowly began to work out the hypotheticals of using the technique in the Super Saiyan state. In the best case scenario, it'd be as easy to use as if he weren't even Super Saiyan. In the worst case scenario, it would be exponentially harder to use in the Super Saiyan state.
But... no... this ain't just the Super Saiyan state I'm using. I've mastered the Super Saiyan. There's no strain on my body from the Super Saiyan no more, so using it... should be just as easy as if I weren't Super Saiyan.
"Cell, you're something else altogether, different from all the enemies I've ever fought. None of them have ever appreciated a really good fight like I do. I guess you being part Saiyan is what makes you like fighting so much. And chances are, I'm only fighting you once. So I wanna make this fight as even as I can..."
If I used Kaio-Ken times two, I would kill him easily. The gap between us isn't that big... unless I were to use a smaller Kaio-Ken? Can I even do that...?
"KAIO-KEN!" A red aura enveloped the Saiyan, his power spiking up to match that of Cell's. Goku was wrong. The Kaio-Ken was actually even more stressful in the Super Saiyan state. He could feel his veins bulging, about to pop. Otherwise, the Kaio-Ken looked as normal.
Damn. "Know this, Son Goku. I do not know how long this fight will last. But I do know I will not stop until you lay dead by my feet."
Exhilarating agony was all that filled his body. Punch for punch, the Kaio-Ken seemed to increase his strain exponentially, with the elation of surpassing his limits negating this.
To think I would ever have to use my full power... damn Super Saiyan.Exerting his speed to his limits, he thrusted his fist directly into the Super Saiyan's face, pushing him backwards comically. He went down, landing on all fours on the tournament grounds and coughing out blood. Cell hovered downwards calmly, his feet meeting the floor.
"Heh heh... is it too much?"
The strain of the Kaio-Ken was unbearable. The veins in the Super Saiyan's forehead and necking were bulging grotesquely, the blood being coughed out of his mouth at the rate of a hose. Damn... I can't go on like this, using the Kaio-Ken in Super Saiyan form. The only other solution is to puff up my muscles, which is even worse...
The red aura wisped away from Son, and he stood up, wiping the blood from his mouth. The golden aura returned. "Heh... using the Kaio-Ken in Super Saiyan was a bad idea. It makes it the opposite of usual. I feel the strain while I'm using it, then it goes away when I'm not. Without Super Saiyan, I bet I could handle Kaio-Ken up to one hundred."
"Quit your incoherent rambling and fight."
Goku wiped the blood from his mouth again, realising that he was speaking with a slur. "I know I'm going to regret this..." The golden aura wisped away as well, leaving Son Goku in his normal state.
What the hell... why is he not a Super Saiyan? Is he giving up?
Son Goku spread his legs apart, held up his fists, and tensed his muscles. "Kaio-Ken... TIMES ONE HUNDRED!"
A massive red aura flared, and the sheer gravity of the immense power left a crater where Son was standing. "Yeah... there you go. This is the true extent of my power, Cell. I never thought I would leave behind Super Saiyan to use Kaio-Ken instead, with Super Saiyan not having the drawback of Kaio-Ken. But right now... it's giving me the power."
Hmm... a technique that raises his power beyond his normal limits, and increases his speed as well. All this without the bulked up muscles. Interestingly familiar... Kaio? Kaio-Ken?
Cell wordlessly resumed the fighting, flying towards the overexerted Saiyan to see if his power had really increased a hundredfold from his regular state. Before he could react, the Saiyan flitted out from the front of him and elbowed Cell in the back, sending him downwards into the concrete arena. Cell's face smashed into it, blood spurting from his nose. Cell got up on all fours to try and resume fighting again, only for the Saiyan to fly towards him and kick him in the throat, sending him upwards.
Cell steadied himself in the air, looking at the Saiyan with disbelief. Damn him!
The mindless repetition enraged Cell to limits he knew not possible. How could such a primitive life-form ascend beyond his power, how could an imperfect being go to this height of strength? The thoughts, envy, and rage were nigh instantly reverted back to imperfect, primal instinct for survival as the Saiyan's elbow smashed in Cell's face, his eyeball being shoved further back into his eye socket and the blood spurting from his nose continuing to increase.
I am more intelligent... than this beast. This idiotic beast! I will outsmart him... yes, I will outsmart him, and I will triumph, because I am truly perfect.
Before he could see it, the Saiyan's fist slammed into the bottom of his jaw, throwing Cell's head upwards and diagonal. With a sickening crunch comically expressing the crack in Cell's neck, two teeth went flying out of Cell's mouth accompanied by a spurt of blood.
Goku stopped and hovered in mid-air as Cell recuperated from the attack. "Damn. Even I'm surprised, Cell. It looks like it's over."
Vegeta crossed his arms and scowled, as he often did. Hmph... that bastard is going to show mercy on Cell or ask him to 'see the error of his ways'... idiot. If this goes bad and Cell catches him off-guard, we're going to have to interfere.
Cell suppressed a deep-throated snicker. The idiot was going to show mercy and it would be the perfect time to attack...
"It's over now. You're designed to be evil, to destroy me. I don't know, if you'll be able to go against the error of your ways, but... I can't take the risk."
Cell, Vegeta, and Piccolo simultaneously shared a look of shock and disbelief as Goku charged up a large ball of ki. Holding the huge mass of energy behind him and thrusting his arm foward, the barrage of energy was launched at Cell. Smoke and dust scattered everywhere, the tournament grounds now completely destroyed. The blast hit at the center of the ring and exploded upwards.
Vegeta stared in wide-eyed shock. What?!... he hesitated! I saw it!
A bloody Cell remained in the aftermath of the explosion, battered but alive. "Ha." Just a short exclamation expressed so much. "You're too merciful, too flawed. You either learn how to fight, or you don't fight at all."
"No, Cell, that's not it," a tired Goku said.
"Of course!" Piccolo exclaimed. "It's too much strain!"
"What? What are you rambling about?" Vegeta asked.
The red aura faded from Goku. "Damn, the Kaio-Ken chose then to catch up with my body...? Heh heh. So close..."
Goku was greeted with a upwards twisting punch to the stomach, making no effort to stop it. Flying upwards, in a semiconscious state from both the pain of the Kaio-Ken and of the battle catching up with him.
"Why is that idiot not going Super Saiyan?!" Vegeta fumed.
"It's hopeless," Piccolo said dejectedly. "Goku was the only one strong enough to combat Cell, but now... regular Super Saiyan won't do any good... it's too stressful for him to use Kaio-Ken in Super Saiyan form, and it's too stressful to use the Kaio-Ken alone."
Holding the bruised, bloody, beaten warrior by his shirt, Cell brought back his left hand and gathered his energy. A luminescent ball of energy materialized in his hand, more than enough power to kill the weakened Saiyan.
He looked at the barely conscious Saiyan with a mixture of indifference, boredom, and a tinge of sadness. Before he would kill him, Cell decided, he at least had to satisfy his curiosity. "Why did you not show mercy?"
No answer.
Once again, he asked. The Saiyan roused. "Wha...-aa?"
"Why did you not show mercy!" Cell asked more loudly this time. "I have a complete compendium of information on you... the Kaio-Ken, for example, which I forgot about until you used it and I searched for the genetic information encoded in my cells. Besides techniques and transformations, I also know your entire personality... the natural Saiyan lust for battle. Your happy-go-lucky attitude... and most of all, your mercy to enemies. Why did you stop now?"
"I..." Goku faintly said. "I made that mistake with Frieza and then he remade himself as a robot..." Goku paused to catch his breath. "And he could have destroyed the Earth."
Cell mused on his answer for a while. It wasn't very bulky, yes, but it was an answer. "Very well. My curiosity has been satisfied. Now, Son Goku," he said with a grin. "Now, I end your life."
Meanwhile, on the rocky bluff above, Gohan, trembled in both rage and sorrow, beginning an increase in power slight but steady. "No..."
Piccolo held him back before he could fly off to attack Cell. "Gohan. Going there would be suicide. You know that."
"No, god damn it..." Tears swelled up in his eyes.
"Gohan! It's over! Goku was the only one strong enough to beat Cell! And now, he's practically dead!"
"Why... why are you... WHY ARE YOU GIVING UP?" Gohan's aura flared tremendously. He swatted Piccolo away effortlessly, flying off to save his father against Piccolo's orders. Before anyone could see what had happened, Cell's jaw was dislocated upon contact with Gohan's foot. Dropping Goku, he reached to touch his bloody mouth with right hand.
"Stupid pest!" Charging up a ki blast with his left hand, he threw it at Gohan, kicking up dust and exploding upon contact. A bloody, weakened Gohan appeared, standing hunched over in the aftermath.
"Wha-?" Cell said shocked. Damn it. I've lost too much energy in this fight. I should have killed him easily if I weren't so tired... normally he wouldn't be a formidable opponent... but if it's him against me in this state, he could damage me seriously.
"Guh-... Gohan!" Goku cried out.
"Silence!" Cell barked at him. "Very well... a child wants to play an adult's game. I may be weakened, yes, but so are you. Come and fight."
Gohan stood there, motionless apart from a slight tremble.
"Come and fight!"
There was still no response from the half-breed.
"Heh heh... just as I expected. My information on you shows that you're not exactly the fighting type," Cell said with a chuckle. "Come on," Cell goaded him. Lowering his arms, his aura disappearing, Cell lowered his defenses. "Come. My defenses are completely lowered. My ki is now lower than yours. Will you do anything? Or do I have to kill someone before you get angry and fight?"
"I... Idiot! Cell's giving him a free shot!" Vegeta said angrily. "That filthy half-breed is even stronger than me, and he can't even fight!"
"Wait, Vegeta..."
Just as suddenly as he had previously kicked Cell, Gohan charged forward, hitting Cell in the abdomen in a corkscrewing punch.
"AAAAAGGGGGGHHH!" Cell choked out. Gohan now stood before Cell as Cell recuperated from the attack, clutching his stomach. "Bastard! Stupid bastard!" Cell raised his arm and struck the half-breed against the face with all the power he could muster. The child was strong in his fits of rage, this he had information on. Now he was very weakened. The half-breed, now laying on the floor from the strike, was kicked in the face for good measure. "He won't be bothering me again anytime soon."
"Now, where were we..." Cell looked down at the Saiyan, lying in the rubble and ruins of what was once the arena of the Cell Games. Having no one else to rival him now, bruised and battered but with still enough power to destroy the Saiyan, Cell was faced with something of an ultimatum, an existential crisis. His ultimate purpose was finally about to be carried out.
Cell's purpose was two-fold: to attain perfection, and to use this power to kill Son Goku. Both of these goals had been encoded in his genetic information by his creator and father, Doctor Gero. But there was something unaccounted for in Doctor Gero's calculation. Cell had within him the DNA of many lifeforms... the changelings, Lord Frieza and King Cold. The Namekian, Piccolo Junior. And finally, the Saiyans, Son Goku and Prince Vegeta.
Perhaps what was unaccounted for was that he had the cunningness and coldness of the changelings, the coolness and calmness of the Namekians, but also the bloodlust of the Saiyans. The desire, the need for a battle. Cell had already attained perfection to the greatest extent he knew of. What was he after killing Son Goku, the only being who had ever rivaled his power? A purposeless being, mindlessly destroying as he would, and what would happen after, with all his power, he destroyed the universe? Perhaps he could find someone as strong as him. Perhaps. But what should ever happen were he to actually be the strongest in the universe, without anyone ever being to rival his power? How then, would he fulfill his Saiyan bloodlust? He wouldn't be able to. He would slowly grow bored, and from boredom springs insanity.
Damn it... am I seriously about to go soft now like this pathetic Saiyan? "Go."
"Wha... what?"
"I shall meet you in one year. We shall have a fair battle, without having to use your obsolete Kaio-Ken. Remember that I shall be training as well, Son Goku. If you are not ready to face me in one year, I will tear apart this universe. Piece by piece, planet by planet, galaxy by galaxy. And nothing will be able to stop me."
"But... but you know if I'm stronger than you... I'll kill you. I won't show mercy like I did to Frieza."
Cell smiled. "I know. That makes it all the more thrilling." As the dazed, open-mouthed faces of the Z-Fighters watched as Cell flew off into the stars, Goku finally fell into rest, knowing that he would live, and that in one year, he would have a great fight before him.