Thought I'd give my 2 cents.
Shorter blade and tryed to define the eye more.
I should work on that eye thing. Thanks for the note on the blade!

I think it needs a more dynamic line of action. Hopefully my image explains what I mean.
I think I get it - the majority of the body in action conforms to the line of action, strengthening the pose. But shouldn't the line of action be running through the sword as well, or does said line only apply to people and not to the objects they're interacting with? I'm not sure, but I think as the hands are holding the sword (and the arms are bolstering the wrists), shouldn't they have more say in how the body is curved? Maybe he could be performing an upside-down U curve? I don't know, please elaborate for me on this!
Also I think if you add how the action is affecting things on his body it will add a good amount of action into the pose. For instance I raised his cape and messed his hair a bit. I gave him a bit more of a reach on his arms because generally when you slash a sword its not so close to your body and your guy kind of seem like was doing a stronger attack so I think it suits it better.
So there's a bunch of secondary reactions going on (hair, cape) owing to the monumentum of the sword being swung. That's actually pretty helpful. Thanks!
(Edit: does the cape in the first picture count as a secondary reaction, seeing as its billowing upwards, or not? Maybe not.)
I'm really liking how these guys are looking, the mock up in front of the building looks awesome though I think the recent image the forsground gets mixed up with the background too much. The second palette looked a lot better to me.
When you say the foreground, you mean the floor the guys are standing on, right? I really should fix that, even if it does mean another palette - it should look more like a proper footpath - with cracks in the floor, dirt and rocks, etc. With the trees and buildings it's a more streamlined background in terms of colours, which is nice - I'm not an expert on the 'guts' and mechanics of the Game Boy, but I'd assume a larger use of palettes at once wouldn't be all that beneficial.