The enemy bosses include a Range-Viper, Metal-Head, Overlord, Voltar, Destro and Cobra Commander himself.

Entity and relation annotations:
id: 0
type: entity
value: text: Range-Viper
labels: <Person>
id: 1
type: entity
value: text: Metal-Head
labels: <Person>
id: 2
type: entity
value: text: Overlord
labels: <Person>
id: 3
type: entity
value: text: Voltar
labels: <Person>
id: 4
type: entity
value: text: Destro
labels: <Person>
id: 5
type: entity
value: text: Cobra Commander
labels: <Person>