There are a few things to address here. For one, your frame placement is the wrong way round; in transitions from extreme points of movement, such as the flip in the middle of the stage, you have too few frames, while you have too many when the guy is in the air. This makes him flip at super speed and then float unrealistically. Try adding more frames for the flip and taking one or two away from the air time.
When he lands on either he hands or his feet, you should show the force by having 1-3 frames of easing, which essentially means you bend his legs and lower his body for a few frames to show the force of the landing before straitening and stretching to show that he is pushing back off for the next flip.
And as for the ramp at the start, I can't really see what he is doing; remember to add more frames than you think are necessary for precise movements like this, because while you know what is happening because you made it frame-by-frame, as a viewer my eyes are untrained and might not catch the movement if it is too quick.
Also, watch the sliding when he is contacting a surface, particularly at the end.
http://www.truploader.com/view/123010 And mine its the colors got messed up i guess the one guys pinkish... -.-
And he keeps flashing... I don't know why
Here again you misjudge where the padding frames should go. You make the guys quickly change their position, then have them punch or kick for three or more frames. Try adding another frame when the blue guy is moving between attacks, and then take out the middle frame when he is actively attacking, which will add force to the blow. Also, after each hit, add a frame or two of the aforementioned easing but stretching the arm
slightly and moving his body
slightly in the direction of the blow. Although when you move his body, make sure to not make him slide. I suggest using the free transform tool and stretch him to the right for a frame or two after each blow without changing his pose.
Watch out for the white edges which break the illusion of the field and make it obvious it is a background. The sun was funny though!