How to Avenge a Teammate's Death in Halo: Reach

Identify the opposing player who killed your teammate. The killer's identity is briefly shown on the left side of your screen above the blue radar display.

Locate your teammate's killer. The player's name will hover above them at all times. It will be red in color, which indicates the opposing team. Their location will also appear as a red dot on your radar display.

Move the reticule onto the identified opposing player. The reticule is the marker used to aim your weapon and is located in the center of your screen.

Press the "R" trigger located on the controller to fire your weapon. You must eliminate your teammate's killer within three seconds of the teammate's death. If you have aimed well and killed the correct target within that timeframe, you will see the "Avenger" medal appear on the left side of the screen above the radar display. It's a gold eight-point star with a red X at its center.