critical has 2 distinct synonyms spread across 2 of its 7 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its 2 recorded opposites are uncritical, noncritical.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
marked by a tendency to find and call attention to errors and flaws
“a critical attitude”
at or of a point at which a property or phenomenon suffers an abrupt change especially having enough mass to sustain a chain reaction
“a critical temperature of water is 100 degrees C--its boiling point at standard atmospheric pressure”
characterized by careful evaluation and judgment
“a critical reading”
forming or having the nature of a turning point or crisis
“a critical point in the campaign”
being in or verging on a state of crisis or emergency
“a critical shortage of food”
1 of the 7 recorded senses carries no synonym, antonym or related term, so it is not shown above. Every sense, with its definition and examples, is on the full entry for critical.
Synonyms, antonyms and the broader and narrower relations for critical come from Princeton University’s WordNet. Full sources and licences.