icky vs rotten

icky and rotten both are adjectives.

Word	Noun	Adjective	Verb	Adverb
icky	No	Yes	No	No
rotten	No	Yes	No	No

As adjectives, icky and rotten are synonyms defined as:

Other synonyms of icky include crappy, lousy, shitty, stinking, stinky.

icky (adjective)	rotten (adjective)
soft and sticky	having decayed or disintegrated; usually implies foulness
very bad	damaged by decay; hence unsound and useless
	very bad