In this run, Acheron's ultimate is used immediately after Aventurine enters phase 2 (he laughs). Due to this, no debuffs are applied and the damage seen is Acheron's damage with buffs only. If you would like to try this yourself, the moment he laughs - you ultimate and (hopefully) he becomes one with nothingness.
More of a meme run, but I've been trying to push the damage ceiling lately. Realized the best defense is an overwhelming offense. Hanya ended up fitting perfectly, pushing Acheron into a 1 turn (x2) ultimate, while providing attack and damage buffs. Even more outrageous when you realize Hanya can use Sparkle's signature light cone effectively... and they stack.
0:00 Fodder Becomes Nothingness
0:20 Buff Stacking
0:52 Opening Hit (Skill Dmg)
1:06 Acheron Buffed Stats
1:40 He laughed (Ult Dmg without debuffs)
2:00 Character Builds