lowest vs worst

lowest is not a noun while worst is a noun.

Word	Noun	Adjective	Verb	Adverb
lowest	No	Yes	No	Yes
worst	Yes	Yes	Yes	Yes

lowest (noun)	worst (noun)
	the weakest effort or poorest achievement one is capable of
	the greatest damage or wickedness of which one is capable
	the least favorable outcome

lowest (adjective)	worst (adjective)
lowest in rank or importance	(superlative of `bad') most wanting in quality or value or condition

lowest (verb)	worst (verb)
	defeat thoroughly

lowest (adverb)	worst (adverb)
in the lowest position; nearest the ground	to the highest degree of inferiority or badness