Joe frazier pushed off his left foot. A lot of guys do this, and, most times, the weight doesn't get back to the right foot. This steals a bit from the left hook- why frazier was a hard puncher, but had to hit you a lot- and the right hand, which is why frazier has a reputation for being a one handed fighter.
Turning your weight ahead of your hands gives concussive force to your punch, like cracking a whip. If your weight is behind your hands you are pushing and, even if you push very hard, it is still pushing.