Frisk & Chara vs Sans (Battle)

This is the first battle in Season 1.

Context
Frisk was almost done with their hard mode genocide route and all they had to do was to kill Sans, so they could continue the route.

Chara was starting to gain control of Frisk and before Frisk was about to press the RESET button, Chara then gained full control of Frisk and fought Sans.

Sans absorbed Frisk's soul, giving him an incredible power boost. After that, they proceeded to defeat Chara.

Battle
We see Frisk and Sans in the final corridor facing each other. Sans starts lining the ground towards Frisk with bones, but Frisk dodges back so Sans blasts them from behind with Gaster Blasters killing them instantly. Frisk loads his last save file, and comes back. They attack Sans with the Real Knife, but Sans dodges, slams them into a wall, and stabs them with bones from the wall, killing them again. Frisk comes back, but this time, Sans reminds them of good times when they weren't doing a genocide run. We see Frisk's soul, getting corrupted by a black substance with Chara in the background. Sans sends several Gaster Blasters at Frisk, but he dodges all of them, and glitches to Chara for a second. They attack Sans twice and he dodges, teleporting into the air and sending Gaster Blasters down at them, but Frisk glitches to Chara and Chara dodges just to glitch right back. We then see a memory of Frisk encountering Papyrus and glitching to Chara for a second just to glitch right back. Papyrus encouters them with open arms just for Frisk to attack him, and we see Papyrus' head on the ground just to be crushed by Frisk. Frisk's soul is getting more and more corrupted by, Hate, the black substance. Sans sends a volley of bones at them, and frisk tries to slash the incoming bones to pieces but gets hit twice anyway. They die, but not before Frisk glitches to Chara once again. We then see many scenes of Sans killing Frisk, impaling them with bones, blasting them to death, slamming them into a ground filled with bones and again. Frisk now wanted to RESET after losing to Sans several times and having regret over their past actions. However, Chara, who had started to be possessed by HATE came and decided to take control of the situation by grabbing Frisk before they could Reset, and we show that Frisk's soul is completely incased in Hate and he is put into a Hate prison, powerless and could only watch the fight. It was proven that Chara was more powerful than Frisk (possibly because they were filled with HATE).

We now see Chara facing Sans instead of Frisk. As Sans sends a barrage of bones at Chara, Chara effortlessly dodges and slashes through the bones and relentlessly attacks Sans. Sans throws Chara at a wall, and lines it with bones, but Chara sinks his knife into the ground, stopping himself. We then see Chara attacking Sans from inside the Hate prison with Frisk in it. Frisk tries to tell Sans "I'm sorry", but nothing happened. We see Chara slashing at Sans, but his movements are starting to slow and it catches the edge of his sweater. We then see Sans blasting at Chara with a Gaster Blaster, and Chara easily dodges it. We then see three panels showing Sans getting more and more tired as the fight drags on. Sans, now very tired, throws 3 more bones at Chara, but Chara cuts through 2 of them and catches the last one, and moves forward for the kill. Frisk smashes the Hate prison wall, and it cracked a bit. Chara was about to kill Sans by slashing their knife at him, but Frisk breaks through the barrier and takes the hit for Sans. After that, Frisk gave their soul to Sans in order to defeat Chara, apologizing to Sans for their past actions. Chara leaps for the soul but Sans gets there first. Sans opens both of eyes, showing a significant boost in power, and shows that he has control over the timeline now, but first, he stabs Chara with a massive bone that leaves them hanging in the air, and blasts them. After defeating Chara, Sans resets the timeline after calling Chara a "Megalomaniac".

Trivia

 * If Sans had not reset after killing Chara, the DETERMINATION he had from absorbing Frisk's soul would have made him melt.