Shame on Him by Sidney Bristol

Black Ops Operative Cale Cunningham is a groomed killer. He knows it. His coworkers know it. And the man who formed him knows it. He’s content to do his job and keep away from polite society because the world needs someone to take out the trash. But now the nightmare from his past is back and the one woman he vowed to stay far away from could be at risk.
Odette Dougherty finally has the life she wants. She has a cool job pushing paper at the FBI, her own place, cats that go for walks, and a successful fan fiction site. The one thing that’s missing is someone to share that with. In her dreams, she falls into the arms of a shadowy man with blue eyes she met a long time ago.
To save Odette, Cale must steal her away from all that she knows. Only then can he protect her from the danger hunting them both. Odette and Cale should be enemies, but a kiss changes everything. Now, Cale has everything on the line to save the one, last good thing in his life.