Being a southpaw I had quite a few KD's and KO's with that punch. I just always hung it out to dry not overextended it. There's lots of powerpunchers in the big leagues who do the same. It's more a balance issue than anything.
I don't think it's the most powerful. I'd give that honor to an overhand right/left for pure, raw power. For sheer nastiness however, due to its stealth and direction, I'd say the uppercut is number one. I just had my orbital fractured by one, so I'm sort of speaking from experience.
Here's a body-punching master that uses the uppercut and the hybrid hook/uppercut [ame]http://www.youtube.com/watch?v=u-VEoFOabRI[/ame] [ame]http://www.youtube.com/watch?v=_fDOH_F_BeA[/ame] [ame]http://www.youtube.com/watch?v=0r0hRugOAHU[/ame]
1 )Because of bone structure. The top and front of the head is thicker. The side is not as thick. 2 ) The hook also has a more of a brain rattling effect, and is more likely to get a sudden direction change of the head.
Without trying to sound like some kinda old chinese philosopher, we can make a case for most of the punches already mentioned but IMO the most powerful punch in boxing is the one you dont see
Where does the uppercut most of the time land? On the bottom of the chin. Its usually a punch thats not seen, in other words the persons neck may be at rest therefore it can be a much more devastating affect when it lands. Its not the most powerful punch in boxing as its difficult to throw for most, and hard to get all your leverage behind it, but in terms of affect it certainly could be the most lethal punch when landed properly.
You can get so so much power into your uppercut, it was the first punch I learnt to throw that I could really rip someones head off when I landed it. You can get your shoulder, lower back, legs, even calves into the uppercut and its just so damn powerful as a result. The best uppercuts have very strong lower backs - Foreman/Tyson/Hamed/Lewis and its as if they are looking to lift their man up with that uppercut Learning to hook brutally takes mroe technique but once learned is maybe just as brutal, especially the angle it affects a chin from and its probably easier to land