Dual Destruction by Kate Hawthorne

Not a villain, but never the hero.
Foster Golden kills people for a living, and with no family and few friends, he’s the perfect man for the job. But distracted by memories of a hedonistic weekend he wishes he could forget, his next assignment brings him face to face with the one man he cannot–the mysterious Sage Rosetti.

Never a hero, and not quite the villain.
Sage Rosetti is no stranger to the shady side of the world. Throughout his life, he’s searched out the deepest corners of the darkest places in the pursuit of his business and his pleasure. When a wink from a stranger leaves him bleeding out in an alley, Sage doesn’t know where to go. He ends up in last place he should be, the arms of the very man who wants him dead, Foster Golden.

You’re mine to own, mine to end.
Against his better judgement, Foster nurses Sage back to health, the two of them rekindling feelings better left buried in the past. Sage and Foster could be unstoppable, but after shots are fired and plans are put into motion, Sage becomes a man obsessed with a desire so powerful it threatens to destroy not just their future, but their lives.