King has a mechanic that is out of sorts with the rest of the boss fights you will have encountered up until this point. After a short chase segment you will be led into a room and King will be raised up into the room.
You'll notice he is surrounded by 4 short pillars, these are the key to beating him.
Lure King into the center of the 4 pillars, and melee each pillar to bring it up out of the floor. Once they are raised, another melee attack it will then become charged (glowing an electric blue) do this for each pillar and King will be stunned for a short period - use this time to melee him or shotgun him. Use your dash as much as possible here to avoid any damage from King.
Slow-mo can be used almost indefinitely on this fight (if you've taken the energy upgrades from the Use Of Weapons skill tree) so keep it up when you can, only deactivating the skill when King becomes stunned so you can squeeze in your damage and save a bit of energy.
After you've done this a few times he will then begin to drop bombs similar to Nerve - if you've been dashing and using slow-mo this won't be an issue, just be extra careful not to dodge into an exploding bomb.
Repeat this a few times and you'll kill King and obtain the trophy.
