Through the Darkness by J.D. Caren

When Analise Brigdon witnessed the murder of her torturer, she thought the nightmare was over, it wasn’t going to be that easy. The police want answers. A new, sometimes harsh, world was opening up before her and the residents wanted her dead. Baylor, a warrior of untold strength, has pledged his protection, but some battles were hers alone.
Baylor is a Reaper—a guardian and executioner fashioned by the Fates. Tasked with protecting those weaker than himself and punishing the deserving, he performed his duty without hesitation. Analise was a human, an innocent, his carelessness plunged her into his world and he vowed to protect her no matter the cost.
As their two worlds intertwine, they discover there are some things even a Reaper can’t fight.