The Purging Trials are half the reason Powerless moves so fast. If you want more contestants-might-die energy, this is the shelf.
Fourth Wing is the obvious one โ Basgiath War College kills its students on schedule, and Violet enters it as physically fragile as Paedyn is powerless. The Violet-Xaden dynamic scratches the exact Kai itch: he has every reason to want her gone, she trusts him anyway, badly. If you've somehow read Powerless but not this, fix that first.
The Serpent and the Wings of Night is the adult version of the trials premise: Oraya, a human raised by the vampire king, enters the Kejari โ a tournament where every other contestant is a vampire who could drain her. The alliance-with-a-rival romance is the best-executed version of 'my competitor cannot be my person' in the genre.
Lightlark structures its whole world as a game โ six rulers, six curses, one hundred days to break them โ with alliances and betrayals rotating every act. It's more puzzle-box than combat, and it splits readers, but the twist density is real. Caraval is the softer cousin: the competition is a spectacle where nothing is what it seems, and Scarlett spends the whole game being played. Less blood, more velvet.