Ire Fist Madrigal

. . . You basically faking springyness this way. Maybe you also want to hold the first keyframe of the punch hitting for 2-3 frames to make it more impactfull

Really good. I find it a little too stiff. What I usually do is: after a fast move, like a punch, I copy the punch move and move everthing just slightly and change the blending after it to Ease In. This way your punch doesn't stop immediately . . .