Axrel by Olivia Riley

A deadly rogue warrior and enemy of the alliance has been placed in her care.

Dr. Charlotte Lockley is taken aboard the military vessel, Tarus, carrying high-risk inmates and ordered to treat those badly injured, including Prisoner Zero–a dangerous vrisha prisoner captured on a human trade world.
As a doctor educated in alien medicine, Charlotte is one of the few that might keep the vicious alien alive long enough for him to be contained inside the max-security prison on the planet Fargis.
Despite his supposed crimes, Charlotte slowly begins to heal the broken warrior. Enemy or not, he is her patient and she will do what it takes to earn his trust.
Axrel as she comes to know him is like a viper–sleek, beautiful, and deadly. Though she’s warned of his killer instincts–and the destruction he could cause if he were freed–he never shows her violence.
Axrel, however, has hatred in his heart. And a need for vengeance against those who have wronged him. But the delicate, strong-willed doctor, soothes his fury. Her touch brings him calm, fills him with a different sort of need that burns as strong as his long-sought revenge. He is drawn to her caring nature, which could be his weakness.
When the unthinkable happens, their fragile bond is tested. Can Charlotte change his black heart or will revenge consume him?