95 synonyms for critical such as compelling, bellyaching, analytic, acute, all-important, and climacteric. Critical is an adjective, and its antonyms are complimentary, safe, and unimportant.
Bellyaching, bitching, carping, castigatory, cavilling, censorious, condemnatory, condemning, criticizing, denunciatory, deprecatory, disapproving, disparaging, fault-finding, griping, hair-splitting, hypercritical, judgemental, negative, niggling, nitpicking, overcritical, pass-remarkable, pedantic, pernickety, persnickety, pettifogging, picky, quibbling, reprobative, reprobatory, reproving, scathing, ultra-critical, unfavourable, unsympathetic, and whingeing.
Analytic, analytical, commentative, elucidative, evaluative, explanatory, explicative, expository, and interpretative.
Acute, chancy, dangerous, desperate, dicey, dire, dodgy, egregious, grave, hairy, hazardous, iffy, in the balance, life-and-death, life-threatening, parlous, peracute, perilous, precarious, profound, risky, serious, touch-and-go, uncertain, and very bad.
All-important, climacteric, compelling, crucial, deciding, decisive, essential, exigent, fundamental, high-priority, important, key, momentous, of great consequence, of the essence, of the utmost importance, paramount, pivotal, pre-eminent, pressing, serious, urgent, and vital.