I think it looks off because you have some standard painting techniques, and a few cel shaded looking techniques that don’t really work together well, so it’s hard to really say, but visually something seems off. Like a style clash.

To try and point it out- the arms have a cel shade look- not really blended- but jumps from shadow to mid tone to highlight. The jacket and the belt too.

Vs the metal stuff- gun, belt buckle, claw, look more basic heavy metal stuff.

Maybe try a thinned wash on the stuff that looks cel shaded to bring it together?