doomed vs ill-omened

doomed is a noun but ill-omened is not a noun.

Word	Noun	Adjective	Verb	Adverb
doomed	Yes	Yes	No	No
ill-omened	No	Yes	No	No

As adjectives, doomed and ill-omened are synonyms defined as:

Other synonyms of doomed include ill-fated, ill-starred, unlucky.

doomed (noun)	ill-omened (noun)
people who are destined to die soon

doomed (adjective)	ill-omened (adjective)
(usually followed by `to') determined by tragic fate	marked by or promising bad fortune
marked for certain death
in danger of the eternal punishment of Hell
marked by or promising bad fortune