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)
Every two seconds creates a area of projectiles around the players that spawn after a second of priming.
Mutation 1
(At 60% hp or after 30s)
More projectiles spawn in a much wider area around the player.
Mutation 2
(At 40% HP or after 60s)
Damage and Speed increases by 150% (from 200 to 500), runs all around the area and creates a circle of projectiles around the player.