At Your Mercy by E. Baileu

Ronan Craig was trained to be a weapon—beautiful, ruthless, and lethal. At twenty-nine, he’s perfected the art of seduction, using his body to lure countless men to their deaths. His latest mark should’ve been easy, or so his handler said. But Wesley Cohen isn’t like the others. One short night, and suddenly, Ro finds that he isn’t in control anymore. Wesley is.
When he meets Ro, Wes sees a dangerously pretty assassin whom he intends to teach precisely what it means to kneel at the feet of an older, stronger man.
Their twisted game of cat and mouse quickly becomes something darker, hotter, and far more dangerous than either expected. For every moment of heat, there’s the reminder: one of them was sent to kill the other.
And when desire turns into obsession, someone will end up on their knees—for mercy, or for blood.

At Your Mercy is the fourth and final book in the Twisted Desires series. You can expect a twenty-one-year age gap, enemies-to-lovers energy, and one very bratty killer.