In Terms of boxing, no haymakers
the jab is the medium ranged weak but fast opener
The jab is used for seting up another and harder strike
The cross is the medium ranged strong but slower opener
the cross is also used for setting up another and harder strike and can stagger an oponent. However, it is not nesassarily used as a fight finisher
The Hook is the close ranged strong and quicker than uppercut strike
The uppercut is the strike that is close ranged, strong, but slower than the hook.
I would say that it is the hardest. it also is great because if you land a solid one the person will most likely drop their arms and stagger a little if not a lot.
However, it is harder to land one and if you dont hit the person you can fall off balance and leave youself open. The reason why we don't see very many people hit or ko'd with these is for the reason that people use them minimally.