This challenge is part of the TNTina's Trial, the second agent that Fortnite's Chapter 2 Season 2 focuses on. You'll have to destroy 20 opponent structures using remote explosives or proximity mines. The challenge itself isn't complicated as long as you know how to use these two items.
Remote explosives — more commonly known as C4 — are of epic rarety. They're extremely effective on structures. This explosive is also simpler to detonate than proximity mines: simply place it wherever you want and then set it off!
The proximity mine — of rare quality — requires the detection of an enemy to be triggered. It's more complicated to use.
Note that the structures to be destroyed must belong to enemy players. There's no way you can disintegrate your own buildings here! Finally, we highly recommend the Team Rumble mode to complete this challenge. You'll have many enemy buildings to destroy at the end of the game, and you can easily find explosives. Plus, you can come back to life as many times as you want.