Also an tip to hit hard is to try to get hold of an dismembered part of uke and slam it into the part you have left in your hand. (this is mostly not at the beginning, or if you make a madman starting with ripping off your own arm)
in my example, i remove an pec and make the rest of the body red and after that i slam the body with my hand that had just let go of the leg, making the head and another pec go off.