To obtain this achievement you need to win a game using an Offensive legend. Offensive legends are denoted with a three bullet logo. Currently, the offensive legends in the game are Wraith, Bangalore, Mirage, Octane and Revenant (the latter three need to be unlocked with either Legend tokens or Apex coins.)
My best advice for winning games would be to find a relatively quiet spot to land with your team and loot up before fighting. Besides that, teamwork is essential. Stick with your squadmates and support them when needed.
z0rrofox confirmed in the comments that you don't have to be alive to get the achievement.