Instant kill with a gun with insane aim assist. You don't need damage reduction when you can instant kill someone from across the room. Counter it? The only thing that can counter an instant kill is another instant kill. Nova Bomb requires an animation. Fist of Havoc requires you to be close. Grenades no. Shotgun no. Sniper? unless you're fast and they don't see you first. Hammers require travel time. It's easier to stop a Sunbreaker.