critical

critical - adjective

marked by a tendency to find and call attention to errors and flaws
at or of a point at which a property or phenomenon suffers an abrupt change especially having enough mass to sustain a chain reaction
characterized by careful evaluation and judgment
urgently needed; absolutely necessary
forming or having the nature of a turning point or crisis
being in or verging on a state of crisis or emergency
of or involving or characteristic of critics or criticism

critical - thesaurus