For the attack, I think the main problem is that he's attacking without any kind of buildup. It takes a little bit of power to swing the sword, let alone make a hit that has some kind of viable impact. His body movements should follow through with the attack, it should take the whole body, including leg and head movements, he seems rather static.
Others can explain much better than I.
For a positive note, I like the motion trails, just clean them up a bit.