OK, well first off your perspective needs a little bit of work. On the left figure one hand is punching towards the viewer, and its the same size as the one by his side. (and pulled back) I'd change the size of the hands (and weapon he's holding) to reflect this. The same deal for the legs. One is clearly in front of the other and should be stretched to reflect this. He's in a dynamic pose, and it needs to look more... dynamic!
The other person looks better, but I have a hard time making out what her arms are. Also her shirt isn't flowing with the rest of her body- you have a line and some button like things going straight down. They should be more like a "reverse S curve to reflect how her torso is moving. If you need me to, I can show you what I mean.