1. dangerous
2. unsafe, breakneck, chancy, chanceful, dicey, dodgy, desperate, harmful, hazardous, risky, venturesome, venturous, insidious, mordacious, on the hook, parlous, perilous, precarious, touch-and-go, self-destructive, suicidal, treacherous, unreliable, insecure, unsafe, vulnerable, grave
2. grievous, serious, severe, life-threatening, critical