Like Phlakes said, the knife attack needs a lot more range...it also looks a little weird how he just...pokes like that. He should be lunging forward with his body and legs if he's trying to hurt something, heheh. The bow attack looks pretty good, but it takes pretty long for him to do it, and it doesn't look like he can do that animation in the air. While that's realistic, I'm not sure if that's what you're aiming for gameplay-wise. Just something to think about.
For your monster death animation, I'm assuming it's supposed to be like a puff of smoke, a la some of the Zelda games. Right now it kinda just looks like a blob growing and dissipating, though. I think it's because there's no real ease-out in the animation - it's basically all the same speed. It should be exploding and expanding very quickly at first, and then wisping away a bit slower once the explosion is over with...here's a little example from me, since I've been wanting to try an explosion lately anyway.
Nothing amazing, but I think it illustrates the point I'm trying to make...I'd check out the death-splosion-smoke effects in Cave Story, too. The guy who made that did a good job with those, I thought.
Edit: Ah, and the monster-eating-his-head animation looks like the monster has teeth and is laughing, because of the strong white. It still reads good enough, I think, but the first think I thought of was a row of teeth.
