I am probably rare because i don't really find all that many FF designs bad or offensive in general, just those that are overtly stupid(like Yuna's ass shorts, who thought that was a good idea!?).
The rest are just ones you'd usually find in Japanese media, either anime or manga. Maybe you just have to like those kinds of designs in general and are not inherently critical of non pedestrian or non 'normal' designs.
The 15 cast has some of the most pedestrian outfits of the whole series and look at all the hate in here. Anything new/popular is cool to hate on I think. Give it a few years and you'll never see Noctis in worst lists alongside Tidus/Vaan.
Cloud is the best. It's easily the most iconic design in the series, and one of the most recognized in gaming in general.
Squall's is completely ruined by his shit personality. Design wise he's good, but holy hell I can't stand that guy.
The worst by far are Vaan and Tidus. There are some other lesser known characters out there, but those two make no sense to me.
I haven't played XV, but I really despise the shirtless jacket guy's design.
In Gladio's superior outfit(selectable by default) he takes off the jacket and rocks a black tank top.
Best:
1. Terra
2. Lightning
3. Noctis
Worst:
1. Vaan
2. Zidane
3. Serah
If including more than just the protagonists, I'd add Fang, Locke and TG Cid to the best and Auron, Vanille and Paine to the worst.