I think anatomy isn't that important for the first step. Even if your sprite would be better with anatomy it would still look boring.
I think the weakest part of your character is the pose. The pose doesn't tell us anything about the character and the skull looks more like pasted in and not as an integral part of the character.
The idea is to find or design a pose which supports the character and it's attributes to it's advantage. This is exactly where my edit comes in play.
I'd recommend to do 10 minutes a lot of quick sketches on paper first with ~20 different poses (each shouldn't take longer than 30 seconds)
After that you pick the best one and work on it digitally (after that you should come pretty quick to a result which only needs a lot of polishing to look ok)
even if you don't like how the charakter comes out at a certain step you can easily redo it or pick another pose from your design paper sheet.
The idea is to find an workflow which improves your drawing step by step. To change some details is fairly easy, to change the basics takes waaaaaay longer.
Next to this I would second to work on proportions, forms and lighting. Especially if you compare your work to the anime and fighting game sprites you use as reference you will find some pretty obvious differencies.
