Some FPS have it where your arms are struggling or doing something melee to a character model. Both the arms and the character you're interacting with are sync'd up in the animation. What's the general idea behind how that syncing is done?
In short, make sure the animations are in-sync when animated, so that you can easily play both animations at the same time. Some systems, like Mecanim in Unity, allow for transitions and so you would have to watch out that the transition does not blend too far in to the new animation. In the same way you'd want to play the animation instantly and not wait for another animation to finish first.
initial animation --> struggle animation --> potentially branch to different animations
It's not too dificult to pull off, but of course requires that the enemy is correctly placed in front of the player. This offset should be the same as when the animation was done in Blender, for example. Generally you have a "root" or "world" object, which is used to position characters at their initial position.
Systems like Mecanim also have some more advanced IK controls, so you can place the arms relative to another point, so that the enemy wouldn't have to be spot-on.
Perhaps if you had a more concrete goal or animation that wasn't working I could guide you a little better. Images of what your character rigs look like as well would be valuable information.