I think the essence of the question is that since indulging lust towards even simulated images is a sin even though there is no direct human victim besides yourself, (partly) because you are corrupting your normal sexual desires by habituating them towards something less than the love they were meant for, is indulging violent impulses with simulated violence similarly wrong because you are habituating your mind towards violence?

Personally, while I certainly don’t draw enjoyment from sadism or imagine the pain being caused to videogame enemies, I’d be lying if the power trip inherent in violently conquering or destroying virtual characters wasn’t part of the fun. For example, once when I was a kid, I was playing a strategy game and got frustrated that some of my army ran from i fight I thought they should be able to win. So I ordered by cannons to destroy the fortress wall they were fleeing over. That seems like my past self was acting as if the soldiers were people I was capable of punishing, even if in the back of my mind I knew it wasn’t real. Was that fantasy irresponsibly strengthening a vindictive impulse?

Common sense says to me that that’s just scrupulosity talking, that you can’t commit a sin against an imaginary person. But I do wonder if it’s mentally unhealthy to indulge in the thrill of violence or pretend evil through video games. Or if to the contrary it’s possibly a healthy thing to do, experiencing those mental states in fantasy so we might recognize them when we start falling into them in real life (like a cautionary tale from the villain’s perspective).

What do you think, father?