I'm sorry... How she hated those words in his mouth. (http://nami64.tumblr.com/post/25028634089/im-sorry-how-she-hated-those-words-in-his) Everything was her fault: her sources double-crossed them and the simple meeting in a car park ended up in gunfight and -his- blood all over the ground, the mark disappearing with the briefcase.

But it was Clint. He has always felt responsible for her since the day he brought back an ex-KGB spy to the SHIELD and Fury said: “Fine, but she is under your responsibility Agent Barton.” Things have changed since then, except him.
She silently swore to rip the heart (and probably some other useless organs) out of this mark.