Board Thread:Questions and Answers/@comment-30546687-20161119211613/@comment-13682699-20161120053846

They probably didn't hate monsters, but they likely did feel betrayed by Asriel's last second refusal to kill the humans attacking them and ruining their plan to break the barrier. Asriel may have done the right thing in the end, but look at what it cost them:

1)they both died and eventually became soulless shells of themselves.

2)they are the main catalyst for all of the issues that befell their family and the kingdom.

3)the barrier still remained after everything

They went through so much and caused so many issues and had NOTHING to show for it.

So ultimately, Chara was betrayed by the one person who he likely cared about more than anyone else, the person who practically personified the monsters' hopes, dreams, love, and future. So if the one person who he cared about still betrayed him in the end, then honestly who's to say that any other monster could be any better? He basically showed Chara that he was more humanlike than they realized (a race which he despises with a passion) So basically, why should anyone exist if they were all so similar.

That's not to say that the player/Frisk doesn't have any influence. If you choose to do genocide, you are teaching Chara that violence is the answer to everything cause honestly, that's all they seem to know anymore.