So this is how I would do it -
First, have the character with a stamina bar. As the character moves around the bar depletes slowly, and recovers fairly quick when standing still. When the character takes a hit, the stamina bar drops by 25% instantly, forcing players to move to safety and recuperate for a second or two.
When the bar drops beneath a certain threshold, say 25% of 100%, certain enemies can do finishers if they get too close.
Also, what engine is this being made in?