Board Thread:Wiki Discussion/@comment-25958552-20160731111602/@comment-34064085-20171224021256

Think about this:

Imagine that you woke up and the last thing you remembered is being attacked by humans, and then you saw a human killing everything it  sees. Well, probably mad. That's exactly how Chara felt. At the time, they had no idea how to control this anger. They kept having to watch monster after monster die because of Frisk/the player, which made their anger grow, and they still had no idea how to control it. The constant growth of anger inside them gives them a desire to let out said anger. It keeps trying to fight this feeling, yet by the time the kill count is exhausted, they've given in to the anger and let it consume them. They're barely able to yank control away from this feeling, and only are able to do so on one occasion:Flowey. Yes, they do regain control for one second, giving you a chance to reset. However, when the player presses z/enter, the anger reposseses them. From this point forward, they're a child who once was good, yet was consumed by their anger that we were killing everything we saw. We, the player, cause Chara to become evil.