From the main menu set up a Deathmatch multiplayer match on the "Fearless" map.
You could get this more easily with another controller as you don't have to be worried about getting attacked.
Find the Invulnerability power up on the map and wait for it to spawn stand where it spawns and then do other things until you get it.
This powerup is located on top of the statue in the main room, accessed by a lift behind the statue.
It takes super powerups around 90 seconds to respawn. So set the match time 30 - 45 mins.
This achievement only requires 10 mins instead of 20 like the others.