Fly in the ointment 

when you are out with a group of friends, this is the guy who always fucks things up. Like when you put antibiotic ointment on a cut and fly gets stuck in it, you say "fuck!"

For example, charlie is a fly in the ointment,

tom: " the guys are getting together tonight, wanna come?"

Charlie: " yea!"

Charlie then shows up with his girlfriend

Fly in the ointment by d-c August 14, 2007

a fly in the ointment 

A minor irritation, or hiccup that makes a failure out of something that would otherwise have been a success.

There is always a fly in the ointment! My ticket matched all six white numbered balls, but didn't match the green Lucky Ball! Still scored one hundred thousand!!! I ain't mad at 'em!

a fly in the ointment by talk2me-JCH2 April 9, 2021

small fly in the ointment 

A flaw or imperfection that detracts from something positive.

The only small fly in the ointment in an otherwise perfect wedding day was the fact that the bride tripped when walking down the aisle.

small fly in the ointment by Hgjw February 14, 2018