History of Blockbuster

Blockbuster is a Gambit medal triumph (5 medals): defeat three Blockers with no more than 3 seconds between kills.

How to complete

Blockers appear on your team's bank when the enemy team banks Motes. Wait until several are up (or a teammate's Block Party setup is happening), then burst them down with high-damage or area weapons so the kills land within 3 seconds of each other.

Source guide is older; current Gambit details unverified.