In this video guide I will show you how to kill three enemies within 10 seconds after restoring full health with the defibrillation. Now you will need to first acquire the defib ability from an ark. The ark is Canyon Cover Ark and it is in the Broken Tract reign. Once you have the ability you will need to upgrade it. Go into the defibrillation and upgrade it to level 5 by holding the X button to buy them. You will be spending 1,000 feltrite to upgrade it all the way. Once you've done that you will need a few perks to use as well to make this work. Press the A button to go into the perks page. You will need the perks reshock level one and two; and avenging aftermath level one and two, if you think you might mess this up or have enough points you can also get the perk cooldown to be able to try it again faster.
Good locations for these would be mutant nests. Since they like to melee and get in close. Unlike goons who tend to stay back more and shoot. Once you find a good nest with decent amount of enemies just run in gather them up by running around a bit. Then let them down you, just press the buttons in the order they appear in. You need to press them when they are in the circle. Once you revive you should be able to kill at least three mutants with the shockwave, if they stuck near you when you went down. And you achievement will pop once you get back up.