The term mutinous describes defiance against authority, akin to rebellion. An antonym would therefore signify obedience and compliance.
Considering the provided options:
Insurgent: Denotes opposition to authority, closely aligning with mutinous.
Recalcitrant: Signifies resistance to authority, similar in nature to being mutinous.
Submissive: Characterizes a readiness to yield to authority, directly contrasting with mutinous.
Observant: Refers to attentiveness but lacks a direct link to obedience or rebellion.
Consequently, submissive is the antonym of mutinous, representing adherence to authority.