This trophy is for getting the Vanquish streak boast at the end of a match. This means you had the longest streak of killing players without dying during the game. Obviously this is heavily dependent on the quality of your opposition and length of game. I got it with a streak of seven during a relatively short game of Gardens and Graveyards but I have seen people finish the game with streaks of 15-20 during longer games. You won't know if you have won until the end of the game, the trophy will likely pop before the scoreboard is revealed.
Tips I have found for long streaks of kills:
- Being a Pea Shooter and defending a capture point while either trying to stay close to a sunflower player to heal you or potting one yourself.
- Being a Cactus and finding somewhere remote and hidden and using the corn strike attack of your drone.
- Being an Allstar (largest health) and attacking a capture point from a distance and throwing in exploding imps into crowds of plants defending a capture point.