"Kill an enemy in a single shot with an 8AP".
How to obtain it: Use a Marine like the Blood Angel Devastator Champion (Tier 2) and a Plasma Cannon. He has:
Scouting: +2AP on first 2 turns.
Charge: +2AP until end of turn, but cannot shoot.
Preparation: Carry over all remaining AP to next turn.
Using Preparation at the beginning of your turn depletes all his 4AP. Next turn, he will have 8AP. Charge the Plasma Cannon with the Secondary Fire Mode and shoot some weakling!