Undertale - Chara's still with you during pacifist

Well, the only reason they ever really got as bad in genocide was your murderous determination. All we really know of them as they really were is that they hated humanity and probably weren't the best possible person.

If they can be spurred to be a genocidal murderer, then perhaps by being a pacifist you could help them, too, turn a new leaf and become a better person? Is that not what the pacifist run is all about?