How to duplicate one frame of an animation?

I have a punch animation with, let’s assume, 5 frames;

the second frame is the punch collision itself. I wanna be able to duplicate this keyframe and move the following frames forward.

I wanna be able to do this when there is a collision. Making the animation slower doesn’t work because it would delay the whole frames.

any tips

Select your animation in the project window inside unity and duplicate it and now select your object with should play the animation, then go over to the window tab > Animation to access the animation window, at the top left corner " I think" there should be a drop down menu with shows all the animations. All of the animations should be " read only" so you cant edit them except the copy that you have made so select that animation and play around with the frames however you want