awing, bad, chilling, critical, dangerous, dangersome, daunting, deterrent, deterring, disconcerting, discouraging, disheartening, dismaying, disquieting, explosive, fear-inspiring, fearful, fearsome, fraught with danger, frightening, frightful, jeopardous, menacing, overawing, parlous, periculous, perilous, scaring, scary, serious, startling, threatening, ugly