yeah, a headbutt might look better with this kind of char anatomy.
the animation is...ok, the main problem here is the lack of body movement. When you punch, you turn your torso sideways and then project your body forward with the arm, that's where the punch strength comes from.
But of course, it'll be difficult to make it visible with this chibi style, I'd suggest you to consider the headbutt, it'll look a lot more interesting.