As adjectives the difference between saggiest and waggiest
is that saggiest is superlative of saggy while waggiest is superlative of waggy.
saggiest
English
Adjective
(head)
(saggy)
saggy
English
Adjective
(er)
Baggy or loose-fitting.
That sinks or droops from wear or its own weight.
waggiest
English
Adjective
(head)
(waggy) waggy
English
Adjective
(er)
having a tendency to wag
Synonyms
*waggily