Speed kills. You'll notice that even some top fighters who aren't very quick can still deliver prety sharp and precise punches... and I don't just mean hand speed. Foot speed, quick upper body reflexes, etc. can all be great advantages in boxing and in any other physical sport for that matter. You can overwhelm even the toughest of opponents with raw quickness.
true :goodbut stamina can get you so far, how many clean punches can one take without a stoppage or long term damage
Stamina. If you can throw 100 punches a round for 12 rounds, you'll put yourself in a great position to win.