From Brotato Wiki
Bosses
Bosses are special enemies that only appear on wave 20. Only one boss will spawn in dangers 0-4 but both will spawn in danger 5. These are the most powerful type of enemy with 29900 health and the player will will the run when all bosses on the wave have been killed on the wave that the boss is on ends due to time. Just like elites they can't be buffed by the buffer enemy.
The Predator
Mutation 0
(initial phase)
Chases the player and dashes. It also surrounds itself in several projectiles. that circle the boss.
Mutation 1
(50% hp or 45s left)
Starts also to emit projectiles in every direction every so often.