I like it!
I recommend ONE shading color for the cape. You're right, it's flat. Although, if the style jives with overall style of the game or whatever this guys is for, it's fine.
The palette is nice - that purple and teal look good.
As for the anim, try some anticipation before the first, or both, sword strikes.
It feels a bit too snappy, and like the sword has no weight to it. He wields it too easily, despite it's size.