oh my god I have these too- for TWO damn cousins. for a few years around middle school I didn’t even want to interact with either of them. I knew they weren’t thoughts I wanted but they just kept coming back no matter how hard I tried to stop to the point I felt like a monster. it’s easier now because I know I don’t want that but they’re still awful thoughts that make me feel awful.
Trying to actively get rid of the thoughts will only make them worse. You can practice thought defusion like saying to yourself “huh that’s an interesting thought.” You can use dialectic statements too. “I have this thought AND I will continue engaging in activities.” Important thing to remember is that you have no control over your feelings and thoughts. You can only control how you respond. Hope this helps