Vitriolic means bitter or caustic; amiable (friendly) is the opposite (Oxford Dictionary).

Insouciant means carefree; angry is a contextually appropriate opposite (MerriamWebster).

Vituperate means to criticize harshly; praise is its opposite (Oxford Dictionary).

Turpitude means moral wickedness; its opposite is virtue (Merriam-Webster).

Quiescent means inactive or dormant (Oxford Dictionary). Vocabulary: Antonyms (Q47–Q52)

Histrionic means overly theatrical or dramatic (Merriam-Webster).

Penurious means extremely poor (Oxford Dictionary).

Effervescent means lively or bubbly (Merriam-Webster).

Obstreperous means noisy or difficult to control (Oxford Dictionary).

Quandary means a state of uncertainty or difficulty, synonymous with predicament (Merriam-Webster).