Crown-of-thorns starfish outbreaks strip living coral from large stretches of Indo-Pacific reef. The starfish carries long spines coated in saponin toxins, which deters almost every potential predator. The confirmed predator list is short: the giant triton, some pufferfish and triggerfish, a few shrimp, and the humphead wrasse.
The wrasse can take them because of its pharyngeal jaws, a second set of crushing plates deep in the throat, and because it will manipulate hard prey against the substrate before swallowing. It also eats boxfish and sea hares that most reef predators avoid, which points to a broad tolerance for chemically defended food.
The causal claim needs care. Reduced humphead wrasse abundance is correlated with crown-of-thorns outbreaks in some places, but outbreaks are also strongly linked to nutrient runoff boosting larval survival. The wrasse is unlikely to be a controlling predator on its own; the honest statement is that it removes some starfish, and that it has been fished down to a fraction of its historic abundance.