unfavourable vs disadvantageous

unfavourable and disadvantageous both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unfavourable	No	Yes	No	No
disadvantageous	No	Yes	No	No

As adjectives, unfavourable and disadvantageous are synonyms defined as:

unfavourable and disadvantageous: involving or creating circumstances detrimental to success or effectiveness

Other synonyms of unfavourable include unfavorable.

unfavourable (adjective)	disadvantageous (adjective)
(of winds or weather) tending to hinder or oppose	involving or creating circumstances detrimental to success or effectiveness
not encouraging or approving or pleasing
involving or creating circumstances detrimental to success or effectiveness