How powerful is the PC? Is the question more about games optimised for mouse+keyboard, or is it about demanding recent games that allows his new machine to flex its muscles?
Since you say he likes Souls-likes Black Myth Wukong probably checks both boxes - I never ended up playing it (my backlog is too long) but it looked great with stunning visuals and I heard good things about the gameplay.
Cyberpunk with full path tracing is still one of the prettiest games out there and a pretty damn good game too after the patches and expansions.
Finally, something like Fallout: London could be an interesting suggestion as mods of that nature are out of reach of the console crowd. Could give him a whiff of what he’s been missing out on.
I love seeing another Unity enjoyer around here. That game is severely underrated and had it not had that disastrously buggy launch the AC franchise could have gone in a completely different direction than the open world RPG flavour we ended up with. Plus, revolutionary Paris is one of the best realized video game cities of all time, it’s just beautiful.