Frisk/Player: Commit 20 genocides in a row, does not use the reset of Chara and use itself determination.
Chara: Hate the genocides Frisk commits, is tired of this.
Flowey: Helps Frisk in the genocide, but have fear that they will kill it some day.
Papyrus: Frisk resets gets a day before he enter, so after the 20 resets, Papyrus still used his "old" clothes.
Sans: Knows all the genocides and is tired of it, this is the one where he gets the souls.
The Other Characters: Didn't change a thing.