Ooooh, this is an interesting question. This is going to be a long answer.
So no, I absolutely don't hate Viktor. Actually, what I love about him is that he has a dark side like everyone else. It's what makes him compelling. Emotionally, he's a deeply traumatized human being. By nature, he's gentle and has a strong sense of justice. Take a character like that and give him a tendency to kill people when he loses control of his emotions, and you've got yourself some A+ internal conflict. That doesn't work if he has no agency in the things he does.
When I refer to a victim mentality, I'm not making a claim that he's not a victim--I'm referring to the fact that he's forgotten that he's not only a victim. Indeed, to some degree, he started out the series having forgotten that people who hurt him can also be victims. To take it further, other people can be his victims. That's just a fact of life about being a human being. It's certainly not his fault that his powers are dangerous, but I don't think it's as simple as him "going haywire." I don't think he's having a panic attack when he ends the world. Actually, I wouldn't be surprised if he did the entire thing while dissociated. That's kinda what it looks like to me.
Now, dissociation is gonna be different for everyone, and I'm not sure if this is how it was intended, but to me, it doesn't feel like I've lost control of myself. To the contrary, I get very intense and goal-oriented when I dissociate. Viktor's sense of reality seems to be distorted, to the point where he is doing a lot of shit he would not have done the day before or the day after, so I would not be the least bit surprised if he was experiencing derealization. If you don't know what that's like...well, you do. If you've had a dream, you know exactly what derealization feels like. It literally feels like a dream. Now I want to be clear it feels like a dream. You are still in possession of all your mental faculties. Unless something else is confusing you, like if you just woke up or were falling asleep, you probably don't literally think you're dreaming? But that's just my experience. I tend to dissociate before and after a really bad panic attack, and as shitty an experience as it is, it's not part of a panic attack so much as it is protecting me from my panic attack. That's the mechanism, anyway. It ends up feeling like something I need protection from.
Derealization doesn't make you do things, but it does impair your judgment in my experience. When things don't feel real, it doesn't feel like there will be consequences to your actions. But, like with being drunk, you're not going to just randomly do shit you would never do otherwise. Like with being drunk, it's not an excuse for doing horrible shit. And while my memory and focus both suck when I'm dissociated, it suuuuper does not feel like being drunk. My ability to reason and logic is still there. My emotions are going haywire, but I'm not being destructive because I'm not a destructive person. Again, I don't have like, the definitive experience here, but it's the only experience I've got to talk about.
Is Viktor a destructive person when he's not losing it? When calm, and confident, under specific circumstances, he can be. He can be very frightening, and use it for the forces of good. Look at his conversation with Marcus. Do you think he was bluffing? I don't. And I think that's super cool, that he recognizes this side of himself now, but knows it doesn't have to be bad, or uncontrolled, or any of the things he feared it would be at the end of s2. He can listen to his emotions, take that sense of justice, and protect people.
A lot of this goes for Allison, too, btw. She was deeply emotionally compromised this entire season, but her actions were her own. None of the Hargreeveses have good emotion regulation (no, not even Five). Viktor's regulation is the worst because his emotions were chemically dampened his entire life. But being dysregulated does not mean you lose control of your actions, or your sense of right and wrong. When you're angry enough, you know it's wrong to say certain things or do certain things, but you're so angry, you stop caring that it's wrong. When you calm down, you feel awful.
Like Five explained to Viktor this season, that is the consequence of them having power. When they make mistakes, when they permit themselves the same moral indulgences other people get to have (like losing one's temper and yelling something one doesn't mean), people lose their lives for it. And because Viktor is very powerful, him lashing out the way normal people do every day winds up getting a lot of people killed. It's not that he's so evil, he destroyed the world. He had a couple of very, very bad days, and instead of screaming obscenities at the taxi driver who honked at him, he flung the entire taxi two blocks and presumably killed the guy. And if it didn't feel real to him at the time because he was dissociated, I would not be at all surprised. But that goes to show that a normal psychological mechanism in someone with powers still has vastly different consequences from what it has in a normal person. It's not that he's gotten correspondingly more evil, just that he pays for his mistakes differently than a non-powered person does.
And that's a hard, hard lesson to someone who dreamed of having superpowers all his life but also cried when his siblings stepped on ants.