:-) What would you suggest ? For hit feedbacks I have blood particles, an animation of them screaming in pain (maybe that's not obvious?), a pain sound, some knockback, though not on alien weapons, and a stun chance, though it's low (depends on ratio between damage and enemy mass)
I don't really pay attention to it anymore, but maybe I should add more blood. It's just I'm not fond in particular of enemies having hectoliter of blood. You know, when you shoot them and the whole screen gets covered in red particles. Or actually, maybe it's just because alien blood is yellow and not red.