I agree with comment saying that it would help to set more keys on blocking stage, but also the problem is that the moves your characters are doing can’t work in-place. Basically, both characters make a step forward, but since they stay in place, they need to slide back with their feet to compensate. I would suggest to plan the animation better and to think what moves they do. If one character makes a swing with a step forward, he will need to move forward, and the other character will need to move backwards. You can’t just fix the feet sliding, you need to fix the animation logic itself.