Mafia III

This achievement is missable depending on how you treat your relations with the three Underbosses throughout the course of the game.

For starters, on the playthrough where you are aiming to get this achievement, avoid doing any side missions for Burke, Cassandra, and Vito. Some players have said that if you want to keep Vito alive, but are completing side missions for Burke or Cassandra, it messes with the achievement.

In order to keep only one Underboss alive by game's end, you will want to play favorites by assigning them all six additional districts: Barlcay Mills, Downtown, French Ward, Frisco Fields, Southdowns, and Tickfaw Harbor. Once you have assigned the fourth district to your chosen Underboss, the other two will show resentment and you will receive a side mission to kill one of them. Then, after assigning the fifth district to your favored Underboss, you will receive another side mission to kill the second Underboss.

The achievement will eventually unlock once you reach the story mission entitled "Yet Here We Are" and only one Underboss is alive.