There is much more to getting the kill than hitting the ball harder. There's placement, there is timing, there is tooling and many other ways to score a point on the attack. But let's admit it, hitting the ball hard is fun. And it can send a message to your opponent that you mean business.
A good hitter doesn't hit the ball as hard as they can every time. It is important to have a change up - like a tip or a roll shot - not only to keep your opponents guessing but also to save your shoulder from certain ruin.
That said, if you want to bang the ball and bring the heat, make sure you pay attention to several things: