He'll cut you up and steal your TV!
NOOOOOOOOOOO I NEED MY TV TO WATCH ADVENTURE TIME!!!
I would jump for joy (not literally, but I would literally shout aloud "This is so awesome!) if, for an episode, something causes Finn and Jake to go all "gears of war" on all the bad guys in a Dr Jekyll/Mr Hyde transformation, as depicted in your splendiferous drawing above.
A transformation would become obvious to viewers by the ruffled hat, detailed eyes and fingers, as well as the chest muscles, similar to the looney tunes episodes where Tweety becomes an eight-foot-tall monster.
...I got a little sidetracked there. Let me refocus on your drawing:
particles are a nice touch: the blood, pieces from his hat, and flakes/hairs on his skin form a nice motion effect as he steps forward to swing his sword.
Facial details are unusual and unique. I'm not entirely sure what motivated you to draw them that way but regardless it looks epic.
His hand pose is uncertain, possibly suggesting that either he has lost his knowledge of using a sword, or he is in a crazed state where he couldn't care less. Presumably the latter.
The lines beneath the pectoral muscles look like his rib cage, suggesting that his muscular build comes solely from swinging his arms. A detail some people might miss, but it's cool if you can recognize it.
Seams in his hat, as well as a knot under his chin conclude the mystery of how his hat fits around his face.
Although it's partially cut off, I would suggest more detail in his legs. Maybe a pocket and more shading.
Love the drawing! =)