https://www.polygon.com/fortnite/2018/6/29/17518464/fortnite-final-fight-teams-12-mode-disabled-50v50

After being added to the game with patch v4.5 on Wednesday morning, Fortnite’s Final Fight Teams of 12 Limited Time Mode has been removed from live servers and replaced with the much more popular 50v50 mode.

Fortnite’s Final Fight Mode, which debuted with a teams-of-20 version last week, has never been the community’s favorite exercise. So, Epic was certainly taking a risk when it decided to run the mode twice in a row, this time with groups of 12 instead. The mode was met with harsh feedback from the community — especially after Playground Mode was disabled only a few hours after going live. Finally, Epic went ahead and removed the Final Fight mode part way through its run, and replaced it with the far more popular 50v50 Limited Time Mode.