Creep Stain
A person who is not only creepy in nature, but then actually does something to excessively cross the line and leave their creep stain mark on your life. Most creep stains make extremely unwanted, inappropriate, lude or aggressive sexual advances in the most awkward way.
"My taxi driver asked if I wanted to cheat on my boyfriend with him...what a creep stain!"

"The creep stain at the gas station told me he worked at the 'Kum & Go' for a reason and asked if he could show me a good time tonight."