This animation is a waste and does not belong on Newgrounds. You're clearly not supposed to upload something like this to Newgrounds, this could have stayed at Spritas and maybe even to Youtube, but work that goes to Newgrounds is not taken lightly as you can see from the previous reviews of other users.
I also suggest you trying to use Sandbag even it it is 'overused', because you just also used the most overused sprite in the entire world. Sonic? Really? You used Sonic but not Sandbag, and decided to substitute it with a green circle. First off, you're also cheating out on the animating that you would have done with a Sandbag, or even a random character, the circle doesn't have any hurt animations, it's just a circle.
Another thing to add, Newgrounds is not the place to upload your tests. I'm sure you won't do it again.