WordNet: baleful, forbidding, menacing, minacious, minatory, ominous, sinister, threatening

Sanatista
threatening or foreshadowing evil or tragic developments; "a baleful look"; "forbidding thunderclouds"; "his tone became menacing"; "ominous rumblings of discontent"; "sinister storm clouds"; "a sinister smile"; "his threatening behavior"; "ugly black clouds"; "the situation became ugly"



baleful


forbidding


menacing


minacious


minatory


ominous


sinister


threatening