Word for a person that's hard to get rid of [closed]

I need a word (or an expression) for a person that you can't get rid of, no matter how hard you try. Like a nuisance, but more poetic I guess.

This person can be called a "bad penny." From The Word Detective:

A “bad penny” is a person whose presence is unwelcome on any occasion, but whom fate perversely employs to torment you by making said person appear (“turn up”) repeatedly, often at the worst possible times. The ne’er-do-well nephew who appears only at family weddings, funerals and holiday dinners, never invited but always mysteriously materializing at your elbow and asking for a loan, is the classic “bad penny.” Former romantic flames can also be counted as “bad pennies” if fortune (or fanaticism) dictates too many accidental reunions (“Don’t stalk him! If you turn up like a bad penny every time he leaves the house, he’ll think you’re a bunny boiler,” Cosmo Girl, 2004).

Although most often used as a simile (he turns up "like a bad penny"), the term is also a standalone noun, as this Wiktionary entry attests:

bad penny
2. (idiomatic) A person or thing which is unpleasant, disreputable, or otherwise unwanted, especially one which repeatedly appears at inopportune times.