sinister vs threatening

sinister and threatening both are adjectives.

Word	Noun	Adjective	Verb	Adverb
sinister	No	Yes	No	No
threatening	No	Yes	No	No

As adjectives, sinister and threatening are synonyms defined as:

sinister and threatening: threatening or foreshadowing evil or tragic developments

Other synonyms of sinister include baleful, forbidding, menacing, minacious, minatory, ominous.

sinister (adjective)	threatening (adjective)
threatening or foreshadowing evil or tragic developments	threatening or foreshadowing evil or tragic developments
stemming from evil characteristics or forces; wicked or dishonorable	darkened by clouds
on or starting from the wearer's left