Personally, I like cute animes where the main character is like "oh no, I made a fucksy wucksy" as she commits accidental magical genocide with fully realized (permanent) consequences, then the story continues fully exploring the changed world moving forward
Bokusatsu Tenshi Dokuro-chan has the cutesy vibe contrasted with brutal and violent murders, though she keeps murdering the same boy over and over again and then bringing him back to life, so idk if that would constitute a war crime. Might be considered torture, so close enough!
Sort athe opposite of PSG where they have cutsey magical girls that curse and sin all of the time but have no consequences. Except for the Phoenix wright episode.
I tried watching Kevin can fuck himself, which centers around an abused wife plotting her husbands murder. It became very clear he was never going to die, so hard pass.
Not an anime, but the web novel Magical Girl Crystal Genocide by RavensDagger is pretty much exactly this. Except Crystal is the only magical girl who doesn't swear, but the series revolves around her anyways, so it's fine.