This is a very simple 10 frame punch
First thing to do is to get your figure into a fighting stance
Stance (Click to Show)
Now you want to have the figure begin to lean forward, move the punching arm back slightly from the fighting stance, and move the non punching arm slightly forward
Lean (Click to Show)
Begin the cross motion the legs do when they are walking, and have the punching arm slightly folded over itself, and move the non punching arm forward a little
Cross (Click to Show)
Have the crossing leg move forward a little faster, and have the punching arm fold over itself completely, leave the non punching arm the same
Full Fold (Click to Show)
Leave both arms the same, and move the stepping leg forward to where it close to touching the shin of the other leg
Close to Shin (Click to Show)
Move the punching arm's elbow 180 degrees, but leave it folded. Pull the non punching arm's elbow closer to the torso, move the stepping leg to where it is almost touching the ground, and have the knee's distance about the length of the figure's thigh
Begin Punch (Click to Show)
Fully extend the punching arm, and move the second arm to where the elbow is slightly behind the back, have the stepping leg make contact with the ground
Punch (Click to Show)
THIS PART IS OPTIONAL
Ease the figure forward for the next 3 frames to soften the landing
Optional Easing (Click to Show)
This is what it will look like when finished
Final (Click to Show)
Hope this helped =)