What are the worst fashion mistakes people make?

Leggings and crop tops look nice on a slim girl, but if you're mother of 5, grandmother of 25, they look awful.

Women who think it's cute to have a fat belly and still wear crop tops or tight shirts with muffin tops hanging over the tops of their pants. Wear a waist trainer for god's sake. And older women like me who wear very low cut shirts and have wrinkled chests. Nothing wrong with wearing tight sexy clothes, and dressing young and stylish, but the wrinkled chest isn't going to get you a hot date.
Men who still wear their jeans hanging down their butt with underwear hanging out. Ugh!

Wearing the wrong size

They don’t look in the mirror to see how they reality look.
Wearing certain new style clothes when there figure is not suitable for that style.

septum piercings look awful

Wrong size of Kickers.

Y fronts worn outside ones trousers.

Things can be confusing when you are pished out of your mind.

Wearing great jeans with boring Tops/tees and no accessories

That brand names equal style

Baseball hat backwards.
Pants down to the thighs.
Low-rise jeans (muffin top)