Sans seemed to be holding his breath, his expression one of bewilderment. He hesitated for a bit before vehemently shaking his head. Flowey was right, and he hated it. He couldn't think of a plausible argument, and he hated that even more.

"Shut up," he snapped, turning away. Flowey beamed and leaned in closer, tilting his head a bit. He'd struck a nerve, he could tell.

"Sans, I might be a bit of a weakling, but I'm not stupid. With the power and knowledge you have? Papyrus, Frisk, and I could have been dead ages ago. You could have incinerated them the moment you found out they'd set foot in the Underworld. Heck, you could've killed me when you found out I was trying to help and guide the humans instead of hurting them. But you've kept us alive," the flower stated, his voice going soft at the end. "Even after you've had so many blatant opportunities... Don't you think that means something? Doesn't that mean Papyrus is right? Maybe-"

"Be quiet!" Sans roared, stomping his foot and causing the ground underneath him to sizzle. "You don't know anything!"

"I know a lot more than you think," Flowey pointed out. "You say you have Asgore on your side, like he's some sort of a trump card- but at what cost, Sans? It's almost like you depend on him. From what I knew, he liked to work alone, just like Toriel. At least, that's what he told you. What was he trying to do again... rise to the surface and take power, right? That was his goal, not yours."

"People can have things in common," Sans bit back warily, scoffing. "What's your point?"

"Even so.. taking over the entirety of the human world would be foolish. They're pretty advanced in technology, even if they lack magic, and there are a lot of them, aren't there? And every human that came down here was too scared to do anything rather than flee, so what did you do? In order to prove yourself to Asgore?" Flowey asked, his voice beginning to waver as indignant tears welled up in his eyes. "You waited for them to come to you, like it was some sort of game! And then you killed them. Who cares about the reasons you used- you killed them! Those poor souls.. But you didn't know what would happen next, did you, Sans? You didn't know about the experiments, not until it was too late."

"I don't know what you're talking about," Sans blurted, taking a step back and curling his fingers into fists to hide the way they shook. He was sweating. "I killed them because they deserved it and because I wanted to. It was convenient- no one tells me what to do!"

"No one but Asgore, anyway," Flowey corrected him bitterly. "Really, Sans, were you that desperate? Injecting determination into human corpses that had already withered away- did you honestly think that would work? That their minds would be sound enough for you to manipulate them into fighting for monster kind?"

"It could!" he yelled back, sweat trickling down his temple. "And it will! We're just-"

"Waiting for the results?" the little flower asked softly, finishing his sentence. His eyes widened, and Sans gave an affirming grunt. "And how long do you think that's gonna take, Sans? You keep killing these humans, but you don't really know what's happening to them after you bring them to Alphys, do you? What was that you said about her earlier- you called her unreliable. Why's that? She's taking awfully long in reporting back to you, isn't she? And last time I checked, Asgore wasn't exactly the patient type. You're scared."

"ENOUGH!"

In a burst of vermillion, Flowey was yanked from the ground once more, rendered a squirming, floating mess as an array of bones circled around him and danced in stiff movements. His lip quivered, but he bit down on it to keep silent. He wouldn't indulge Sans by cowing away, not now- he'd been so close. He was going to say it even if it killed him. Flowey spoke rapidly even as he ascended, the red magic surrounding him turning the cave walls bloody.

"And that's why you're attacking me right now- because you don't want to hear the truth! Because you're scared! That's why you were fine with Frisk killing you earlier- it was an easy out!" he yelled, never tearing his gaze from Sans' dripping face. "That's why you wanted to kill Papyrus too- just in case, right? Who would notice if you switched a human body for a monster one? If it worked in the end, it would be a win-win anyway! But you were afraid it wouldn't work! You hesitated!"

A spiraling bone slammed into Flowey's head and he grunted feebly, trying to blink the stars from his eyes, his world momentarily flickering.

"I-I wouldn't do that again, if I were you," he slurred, causing Sans to let out a bark of shaky laughter.

"Or what? You'll lecture me to death? Real scary."

"Not as scary as a failed experiment."

Sans paused, the bones in the air coming to a slow standstill. The tips of his fingers quivered, and he squinted. "...What?"

His voice seemed to crack a bit at the implications of Flowey's statement, and the surface of the gooey pool below rippled sluggishly with the tension in the air. Flowey blinked slowly and stared fixedly at him, his gaze hard at first. Then it turned into one of pity. Understanding.

"It didn't work, Sans," he whispered into the deafening silence. "Why else do you think Alphys doesn't want to report back to anyone...?"

"Th-that's a lie," Sans sputtered, shaking his head rapidly. "You're lying!"

"Why would I lie to you?" Flowey pleaded desperately. "After trying to help them this whole time, do you really think I would just go missing and abandon my friends like that? I snuck into Alphys' lab, you idiot! I SAW EVERYTHING!"

His cries echoed off the walls painfully, making the water below slosh. The red magic subsided, and Flowey fell to the ground with a relieved but pained whimper, thrusting his face into the mud purposefully to hide his tears as he shuddered. Sans stared, his form going limp. He couldn't think of anything to say.

"It was terrible.. they were gone. Every last one of them- not even able to talk properly, and their eyes, just dead.." he lamented. "It's like the amalgamates all over again. She failed, Sans. It's all over. Asgore's plans fell through...You can escape him and become allies with Pap and Frisk, and..You don't have to be scared anymore."

Sans gawked at him, slowly shaking his head as beads of moisture rolled down his face. His jaw clicked as it opened, but no words came out. There it was. The words he'd tried to keep from the air had been spoken, and they'd crushed him with their shaming weight. The truth he'd been shying away from was now right in front of him. The lights in his eyes faded until his sockets were pitch black.

It had all caught up to him.

Flowey's choked whimpers and sniffles were the only thing that permeated the air, and even after he'd finished crying, too weary to spill further tears, Sans still couldn't find words. Instead, he fell onto his knees, hunching over, his fingers digging into the mud ruefully. His world had just been taken out from underneath him, his vision was blurring, his magical core was pounding hard against his sternum so hard it hurt.

Everything hurt.

"I-...No," he squeaked. "No, you can't.. I can't go back, I.. Everything that's happened, I can't just..What've I done? What've I done, I can't just..I've come this far, we..I can still.."

Flowey sat up slowly and stared, bleary eyed and exhausted. He gave a shuddering sigh and slouched, leaning towards him gently. Despite Sans' tyranny and mistaken ways.. he couldn't just leave him. That wasn't what he'd come here for.

"...It's time to give up, Sans."

So basically sans was realizing really quick that HE was the one going soft. Tried going to Asgore to toughen himself up, and Asgore made him kill some humans as a sort of hazing. But it turned out it was the plan all along, and he had to send them to Alphys, who was injecting determination into dead bodies to reanimate them and 're-program' them to fight FOR the monsters. A building of an army of some sorts. Sans called Alphys unreliable because she was avoiding communications with him, and taking forever to report to Asgore, who was getting impatient. And surprise..

Sorry if it's not as quality, and it's very dialogue heavy.. it was a hard chapter to write.