Lovely Corruption (previously published as Undercover Attraction)

Chemistry and hate burn like wildfires when two enemies fake their engagement in the fifth book of the O'Malleys series by New York Times bestselling author and TikTok sensation Katee Robert.
  
Ex cop Charlotte Finch used to think there was a clear line between right and wrong. Then her fellow officers betrayed her, and the world is no longer so black and white. Especially when it's Aiden O'Malley, one of the most dangerous men in Boston, who offers her a chance for justice. The only catch: she'll have to pretend to be his fiancée for his plan to work.
 
Aiden can't afford to let anyone see the man behind the mask. To run the O'Malley empire, he has to be cool and controlled at all times. But the moment he meets Charlie, they're playing with fire. Her slightest touch is enough to send him over the edge. At first their "engagement" was a way to eliminate his enemies. Now he'll do whatever it takes to keep her safe—even if he has to destroy his own family to do it.