slepac

1. blind man; blind person
   Slepac je prelazio ulicu sa psom vodičem. — The blind man was crossing the street with a guide dog.
2. derog. someone blind to the obvious
   Kakav sam slepac bio, sve se videlo! — How blind I was, it was all so obvious!
3. colloq. derog. incompetent person; loser
   Ma pusti ga, on je običan slepac, ništa ne ume da uradi. — Forget him, he's a hopeless loser, he can't do anything.

Slepa osoba is the more neutral and polite expression.