Once You're Mine by Morgan Bridges

Murder brought us together.
Only death can keep us apart.
The Tormentor:

Calista belongs to me... she just doesn’t know it.
The first time we met, I wanted her.
The next time, I was obsessed.
I watched her.
I followed her.
It only deepened my need to possess her.
Once she's mine, I'm never letting her go.

The Target:
Hayden Bennett is a monster, in and out of the courtroom.
Unfortunately, I need his help.
What was supposed to be a simple transaction turns into something else.
Something intense.
He’s always there when I need him,
but I don't know if trusting him is a good idea...

Once You're Mine is Book 1 in the Possessing Her Duet that ends on a cliffhanger. It contains a morally gray hero that's OTT/JP, a stalker who falls first, has Touch Her & Die energy, and is willing to do whatever it takes to have her.