If you are the type of player who has trouble generating power when looping, try out these two tips, and you'll be surprised at the improvement.
First, keep your legs farther apart, i.e. a wider stance. This makes it easier to transfer weight into the shot, meaning more power. Watch videos of the top players and you'll see how they all keep a pretty wide stance.
Second, contact the ball more from your side. Many players contact the ball too much in front of their bodies, and so they get power mostly from their arms. By contacting more to the side, you get more natural body rotation into the shot, meaning more power.
Third, tilt your wrist slightly back. This will naturally give you more wrist in the shot – and you'll likely use more forearm as well as you use it naturally to snap the wrist into the shot.
By following these three tips, you'll get more power without really trying since none of these involve trying to "muscle" the ball – it's all about good habits that allow you to maximize your natural power.