One that offends all around them with their aura of cheap fragrance. One that molests passers-by with a pungent force field of Axe body spray or similar over indulgent smell-weirds.
A hardo is a person who tries extremely hard at everything. Most times a hardo will try very hard at things that do not require excessive effort. For example, sports practices, gym class, etc.
Wow did you see Jack at practice today? What a hardo!