Bongo (known as Isao in Bare Knuckle Mobile) is the boss of the fourth stage from Streets of Rage and Bare Knuckle Mobile, and in the survival mode of Streets of Rage 4. He is replaced by Big Ben in other games.
Bongo appears as a large, bald and obese man of Asian descent wearing suspenders. His moveset entails only running diagonally across the screen breathing fire. Grappling Bongo is a bad idea, since he is so heavy that he counters nearly all throws by simply landing on the player, causing massive damage.