Hiya. Octabox here.

As a newbie in animation, I'm finding it hard to animate the reactions of the person I'm bashing up.
While my offensive character looks half-decent, the actions of the reaction character always looks choppy and really rushed.

Is it because I'm doing offense and defense separately?

If I didn't make myself clear:
Offense punches Reaction in Frame X, then punches him again in Frame Y. That would mean I am forced to produce a smooth transition for my Reaction in between Frames X and Y, so that Reaction can be "where to be" in Frame Y.

Here's one example of where Reaction was rushed (my first animation):
http://www.fileize.com/files/7ba36a12/a4d/First_Attempt.swf

See how to blue guy's steps were rushed? For someone who's getting beaten up, his feet still move very quickly. But if I made took up more frames to make it slower, then he wouldn't be in the right place to get tackled!

And this is the animation I am trying to do right now:
http://www.fileize.com/files/5eb4b8f8/6af/Attempt_No_2.swf

How would I need to modify anything so that I do not make the same mistake here?

To all those who were willing to read through this: thank you. I really appreciate it.

Quote from Octabox

Is it because I'm doing offense and defense separately?

Yeah. Your first animation doesn't look bad, but you're animating each move like 5 feet in front of the last one, making it look like there's a ton of force behind them. That's why the reactions look rushed, if someone is punched that hard they're going down, they're not just going to get knocked that far backwards and still be on their feet.

Try animating everything together and see if that helps. This is the sort of thing you'll figure out with practice.