The Strongest in the Galaxy (Allegedly) (Mates and Mayhem in the Imperium, #1) by Veronique deSol

He thinks she’s the most dangerous thing in the galaxy. She thinks they’re friends. They are both correct. Lily has killed exactly one person, stolen exactly one spaceship, and is having, by her own estimation, an excellent year. After spending two galactic years stranded with only her ship’s AI for company, Lily finally lands a job aboard a luxury alien vessel. She wants stability. A fresh start. Maybe even a friend. What she gets is Khar. Former Intergalactic Legion warrior. Apex predator of his species. Completely convinced he’s the most formidable being in every room he enters. He’s not wrong. Until Lily accidentally starts ruining his life. His unbeatable gym record? Gone. His flawless work performance? Hers now. His peace of mind? Rapidly deteriorating. Forced to work together, Khar can’t decide what’s more dangerous: her effortless ability to outperform him at everything… or the fact that she has no idea she’s doing it. Lily is just excited to have made a friend. Khar knows better. Because for his species, attachment isn’t a feeling. It’s biological. Permanent. Possessive. And once it begins, there’s no stopping it. As danger closes in and Lily’s past catches up with her, Khar must decide whether to protect the woman destroying his carefully controlled life, or lose her forever.