It takes a bit to decide on the desired action and the rest of it is not that complicated - just bunch of modifications of a few frames.
I cant tell for sure - I've done it over a weekend along with other stuff. Roughly 6-8 hours maybe.
I love how it has the exactly right amount of frames! And so dynamic!! 
If it's not a secret, how long does it take you to create such an animation (if you do it himself, not in a collab)?
Hey, how about give him some teeth? Great job overall, no doubt, but he looks kinda old without grin.
COOL!!! Maybe they could make an appearance in Mortal Kombat!
Fantastic work as always!
Rage-Jiggle! :)