As adjectives the difference between faggiest and naggiest
is that faggiest is superlative of faggy while naggiest is superlative of naggy.
faggiest
English
Adjective
(head)
(faggy) faggy
English
Adjective
(er)
(pejorative, informal) Effeminate; homosexual; gay
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naggiest
English
Adjective
(head)
(naggy)
naggy
English
Adjective
(er)
Prone to nag, irritable