Moonstruck

Atticus Mulvaney is the eldest son of eccentric billionaire Thomas Mulvaney. Like his brothers, Atticus is a psychopath, raised to right the wrongs of a broken justice system — but unlike his brothers, he's not very good at it. Jericho Navarro is a vicious killer who, to most, is just a mechanic, but to a ragtag group of social misfits, he's the one teaching them to eliminate those who prey on the weak.

When Atticus and Jericho come face to face over a shared enemy, their accidental meeting ends in an explosively hot hookup neither can forget. As Jericho's mission bleeds into Atticus's life, two separate but equally brutal families have to learn to fight together to take out a common enemy — but no amount of brute force can show Jericho how to scale the walls of a psychopath's heart.

Moonstruck is book three in the Necessary Evils series, a high-heat, intense romance between two dangerous men, with an HEA and no cliffhangers. Each book follows a different couple and can be read as a standalone.