The formula for momentum (what determines the energy contained in a moving body) is P = MV, where P is momentum, M is mass, and V is velocity. In general, the speed at which human muscles can move does not change with the size of the human involved. Mass, however, does.

So, all other things being equal, such as fitness, nutrition, and technique, a man who is 30% bigger will produce a blow which has 30% more momentum. It's worth noting here that momentum also informs your ability to take a punch, for the exact same reason. You're 30% larger, and have bigger bones, muscles, etc, and you can better absorb the force transferred from the punch to you.