ZHEROS

If you are not already aware, this will apparently not unlock if you're playing coop, meaning that you have to play three playthroughs in total. The DLC is included in this achievement for some reason, so you will have to buy it to be able to unlock this. I got through on medium by upgrading the gun first, fists second and shield last. The gun can clear out a room of small enemies when fully upgraded, which is immensely helpful and allows you to focus your fists on the larger enemies. I basically got by with spamming and cancelling the animation for the final attack in the combo by pressing , before starting a new combo. When the more powerful spamming combo is unlocked (....), use that instead. There are probably other helpful combo's for AoE or knockback, but I couldn't be bothered to remember them while playing. The shield is a life saver though! Always keep an eye out for shots to reflect or hits to block. Shoutout to the walkthrough of this game as well, it is full of useful strategies.

Oh, and make sure to play as Mike.