Mine is sometimes pleasant and bright, but many times it is dark but never what I'd consider truly evil - any violence in these thoughts is reactionary because I was provoked in a serious manner. Just dark thoughts about adversaries, people denying me important things, losing things or health problems caused by someone else's actions or omissions, bullies, and killing/fucking them up when I fight back, bad power dynamics, taking adversaries to court, wanting to sue to living shit out of them until they are bankrupt, homeless and destitute, and even self-destruction and suicide, and of course, the most savage violence you could ever think of, even if it was provoked and I was at my wits end.
Trust me, it is not pleasant. I try not to think about these things, but they have a nasty tendency to creep into my mind.
Seeing a doctor about it probably won't help. I wouldn't even confide these thoughts to a counselor because I am afraid I'd intimidate them in some way.
This all stems to the way I was treated as a kid.