B.I.O.W.E.A.P.O.N.

B.I.O.W.E.A.P.O.N., also known as the BIologically-Omnipotent Weapon of Elimination, Annihilation, Plagues, and OppressioN, is a Boss Bloon that appears in BTD7: Planet of the Apes.

The Black Death
Infect 5 towers on the screen with a deadly plague that kills them within FIVE SECONDS. Other than spamming healing towers, the only way to stop them from being killed by the plague is by selling them! Once they die, they infect other towers within THEIR RANGE!! Super Monkeys, Monkey Flashes, Shield Generators, and Monkey Zombies are immune. BIOWEAPON gets back 5% health per tower killed by the plague. Towers killed by the plague CANNOT be revived.

Trivia
An obvious reference to the Bio-Weapon, an exceptionally lethal pathogen in Plague Inc. that kills everything it touches.