There’s a lot of questions about the exact nature of how a SOULless being changes in Undertale. There are some important underlying questions that we have to ask ourselves about them, as people. Are they the same person that they were, before their death and resurrection? Does their consciousness remain intact? Are they still responsible for the choices they make, as a result of their SOULless nature?
Like, there is a lot of continuity between Flowey and Asriel and back again, as he turns from one to the other. We can’t accept that being SOULless makes one a terrible person by default. It doesn’t work … Or else, why would Flowey try to appeal to Chara and ask them not to do it all again, when the game is restarted after a pacifist playthrough … ?
It implies that SOULless is not a transfiguration of the self, but a lack which, over extended periods of time, can distort the self. Perhaps there is more of Asriel in Flowey than we think; the heart of everything that Asriel does as Flowey is play.
Without empathy, he perceives the people of the Underground as his toys, and the fallen Frisk as his playmate. What would he have looked like, had he had a soul? Would he be the innocent muffin that we see depicted in th fandom, or would we see a harmless trickster kid, moving along from one game, one prank to the next? Without empathy to give him guardrails, the lives and pains of others are rendered meaningless.
On the other hand you have Chara. If you accept that they partake, at least passively, in all runs, then you need to also need to accept that being SOULless doesn’t necessarily make them evil. But in the Worst run, through the narration we see in a Chara that becomes more active, a profoundly literal mind, deeply focused on a singular purpose.
The Chara who we speak with at the end of the Worst run doesn’t use the same kind of language that Asriel does. They don’t refer to to the world as a ‘game’ or to having ‘fun.’ They’re very existential, and instead refer to a mission, and seem most happy with discovering a purpose for themselves.
I think that, too might be a corruption of the person Chara once was. Is it not impossible that in life they might have had this same practical outlook, devotion to a mission which was then guided by their compassion? A compassion which, once gone, rendered them rudderless until they found an alternative solution?
Just a few thoughts I wanted to throw out there.