Is the uppercut the hardest punch in boxing?

That has to travel up so I assume it's usually the overhand right

 

If someone knows to put leverage yes I think so.

 

Uppercuts seem more painful than they are, as long as you see the punch coming that is. Why uppercuts are so deadly is because they come from a low angle, and thus more often land without the recipient seeing the punch coming. The magic of a blind spot.

At least that is from personal experience. The only times my head has been rung like bell in the gym were with right hands; looping, straight, over-head.

 

Ruddock,s smash "left hook"comes to mind

 

No, it's the cross. A straight one. For most boxers.
Overhands lose momentum. Mass times acceleration.

Some techniques / body types could make a very charged, full torque hook or upper exert the same force, give or take.

In terms of what hurts the most, a precise hook to the liver.

 

The hook is the hardest punch that can be thrown given you can throw your entire body weight into it. Even an untrained fighter can throw what I like to call a "club punch"........think Wilder vs Stiverne 2 in which the punch travels a great distance building up speed and force to do ultimate damage.

Obviously depending on your training and what you work on, you can make certain punches in your arsenal be extremely dangers, but as a common punch thrown by all fighters, I'd have to say that the hook (and/or an overhand) are the hardest punches thrown by a fighter.