From Halopedia, the Halo wiki

Ninja redirects here. For the multiplayer medal represented by a ninja, see Beat Down. For the Halo Infinite medal, see Ninja (Halo Infinite).

Ninja is an achievement in Halo 2 (Windows Vista). It is worth 20 Gamerpoints and is awarded for killing 5 people by melee from behind in a non-team game.

It is represented by a gold eight-pointed star with the face of a ninja in the middle.