Chara was never "murderous" in life. The only person they killed was themselves. And they tried (not succeed) to kill 6 humans for greater good. Whatever or not they felt guilty is ambiguous. They do say that they have to be "strong' in order to do this however, showing that they did feel bad to do this. There's no evidences that they had no remorse at killing the 6 humans to free the monsters. You're extrapolating things right now and jumping into conclusions.

Also how in the lore murder can bring dead people back to life?? Where was it ever stated?? The power that brings dead people back to life is said to be dt, not murder.

Also, you name Chara at the beginning of the game. The game says "name the fallen human". It does not ask for our name. Absolutely nothing implies that we're Chara. Chara is a separate character from us. And their name is present in the pacifist run because they have always been arround, which is also confirmed by their memories.

Just because they explictly manifests themselves in the genocide run, that doens't mean that they aren't present in other runs. In genocide run, they see you as their best friend as you prove them that Asriel had betrayed them so they no longer hides that their identity as the narrator or another entity in Frisks body.