The Sideways has some tough opponents to tackle.

Fortnite Season 8 has been soaring in constant updates since it was released around a month and a half ago, and now player's are trying to chip away at their battle pass in order to max it out before Season 9.
One of these ways is to complete the many quests within the game, and the Sledgehammer quest line will task players with defeating the Boss Cube Monster.
Boss Cube Monster Fortnite Guide
The Sideways is where this quest will take place, and if you don't know where to enter The Sideways, you're going to want to make your way over to the area surrounding Holly Hedges.
Once there, you should see some funky looking materials around the group, and there will be a portal that you'll be able to enter while will take you to The Sideways.
Once here, the main part of the Sledgehammer quest is going to task you with defeating the Cube Monster, and player's have been having some difficulties with this boss.
The main issue when taking on this boss is the wide array of attacks it'll throw at you, considering the size and statue of this boss, we recommend taking it on from a distance.
However, they don't have a lot of health and you should aim for the large weakpoint within the body of the monster. This is indicated by the glowing hole near it's mid-section.
Using a Scar or a Mini-gun will quickly decimate this enemy, and you'll quickly find yourself completing this quest.