While Fortnite has a multitude of famous hero skin from Marvel and DC, Epic Games also included a generic Superhero Skin which allows players to change the color. One of them is black, and as you'll see, it can be hard to see in certain scenarios. Redditor u/Pricytoaster posted a photo of a player in a dark room facing a bookshelf. Next to them is another player using the black tint of the Superhero skin.
It's so dark that the player can't even see them, including most of the people on the post. You can take a look yourself.
The community has immediately started complaining about the integrity of the game since the Superhero skin has to be purchased. And if players can hide more easily from enemy players it gives them an advantage, and if it's behind a paywall. They have a good point.
The reality is Fortnite has never been about fair competition, it's been about fun and creativity. One only has to look at the multiple additions throughout the years, some right before a massive tournament, to know that Epic Games doesn't care.
So complain and moan all you want, but Epic Games has continued to show they're not worried about the competitive part of the game and that would include and "unfair" skin.