Unstoppable (or Immovable Object in Halo: Reach) is a multiplayer medal awarded when any player kills ten opponents in a row as the Juggernaut without dying in a Juggernaut game variant.
It is represented by a bronze five-pointed star with a green MJOLNIR helmet with outward-pointing spikes.
This medal is very hard to achieve in Halo 3'sMatchmaking because Juggernaut matches only go up to 10 kills. Killing the Juggernaut to become one will add a point to a player's score, but since he/she was not the Juggernaut at the beginning of the game, it will not count as one of the 10 kills needed for the medal.