@lu22 When you think you are evil, maybe try correcting yourself. "I have OCD, and I am suffering because of it."
Also, what does it mean to be good? Personally, I don't know you. But I know for sure that nobody is perfect. Nobody has good thoughts only. Not even people who don't struggle with mental illness, not even the most extreme pacifists. Good and bad exist on a spectrum. You don't have to be a horrible person to do bad things. And you don't have to be a saint to do good things. Same goes for thoughts.
You can be a person who always follows the law and is kind to anyone, and think "damn, I want to punch/kill this guy." You can have that thought, and even enjoy the thought. I have. I never hit anyone, but sometimes, the thought of punching someone feels good. Sometimes, people fantasize about killing their exes for cheating on them. Both these thoughts are not good. But they don't make a person bad, even if they enjoy the thoughts. What makes a person bad is, many would say (including myself), acting on those thoughts.
Sime folks have violent thoughts and may find themselves liking those thoughts. They may even create detailed scenarios in their mind. These people don't feel bad for their thoughts. And that is ok. They like them, don't act on them, and move on with their life. If you think this category is evil and horrible, then 99.9% of human beings are evil and horrible and we are all doomed to an eternity in hell.
Then there's people who have the thoughts, and find themselves liking them. No guilty feelings, no stress. They're not even intrusive, they're wanted thoughts. These people will have no problem acting on those thoughts. The only source of anxiety, for them, may be getting caught. I think most people would call that evil. I think we are all the result of our experiences and brains, and even among these people, there are those who need help.
Then there's people like you, who experience violent thoughts and feel like crap because they don't know if they enjoy the idea of doing that thing or not. That is okay, it happens, especially with OCD. The thoughts, no matter how violent or recurring, don't necessarily make you evil. It would be enough to move on with your day, but you do more than that. You are so scared of being evil, that you torment yourself to protect the thing you care about. You spend hours wondering if you are evil. This experience doesn't make you a bad person, but a person who needs help.