Committing "Horrible" acts? Are referring to that scene where Haruto was overcome by desire in a "Vampire" state? From what I've seen, he doesn't even know what he has done.
If you get drunk and kill somebody, you probably won't remember what you did. You may not hold anything against them and deeply regret your actions, but you'd still be legally held accountable for having killed another person. Why? Because nobody
forced you to enter a drunken state. You
chose to drink enough alcohol to become drunk, and you're responsible for knowing what being drunk means.
It's the same with Haruto's vampirism. Think back to the first episode.
He agreed to become like this. He is a guy who was presented with the question, "Do you resign as a human?" and instead of going "Wait, what the ****? No!" he was so wrapped up in his feelings at the time that he just clicked the "Yes" button, mindlessly, so the damn robot would hurry up and turn on so he could start killing people.
If you agree to a contract without reading it... well, for one, you're stupid. And man, Haruto is
really stupid. But two, the
contract still applies. And the fact that Haruto is the type of person who would say "Yes" to "Do you resign as a human?" to get what he wants is the central trait of his character. And in 99% of all other fiction, anyone willing to do stuff like that
would be the villain. In that moment he was so angry he just wanted the power to hurt the bad guys who hurt him, and he
didn't care about the consequences. He was being a massive hypocrite and proving that everything L-Elf said about him was absolutely correct. When faced with a real conflict, all of his protestations of pacifism flew right out the window. In the heat of the moment, he only cared about making himself feel better.
And that's what it goes back to with Haruto in Valvrave, over and over again. He regrets it when things turn out badly (for him), but every time he's given the chance to make a decision, he never thinks about the wider world or other people. He thinks about himself, only himself, and what will make him happy in that moment.
Only realizing it after the fact. He even tried to make up for it by asking Rukino to marry him....
Only someone who is a
tremendous asshole, I mean like the most mind-blowingly self-centered person in the world, would think that made up for anything! So I was entirely pleased that was his reaction. What the **** was he expecting to hear? "Yes, Haruto, I totally want to spend the rest of my life with a man who at any time can explode into bursts of uncontrollable violence that will most likely be directed at me"? Haruto's literally asking someone to become his goddamn battered wife! It's just more proof he never really cared about Rukino's feelings, or anyone else's feelings, and is just worried about satisfying himself.
As for "why isn't he trying to get rid of/stop the power?" ... Well, er, because it's kind of a necessary evil right now?
Also, because he's selfish. Before Haruto had the power, he was a milquetoast wimp literally anyone could push around. Now that he's a vampire, he's literally the most important person in the world! He's strong and can do whatever he wants to whoever he wants, and they could never stop him. Haruto keeps using the Valvrave for the same reason a man who gets drunk and beats his wife keeps getting drunk.
Because it makes him feel good. And even better, Haruto's powers make him famous! He has literally millions of friends, and everyone thinks he's a big damn hero and praises him constantly. L-Elf, the character who directly pointed out what a useless pile of crap Haruto is in the first episode, has now made Haruto the center of his life. It's very obvious that Haruto doesn't actually care about saving or helping anyone, beyond the fact that it makes them indebted to him. Haruto doesn't care about good or evil. At this point, he just enjoys being a celebrity, and he does all manner of superficial things (
like ask the girl he raped to marry him!) to try and make sure that celebrity doesn't go away.