It's the violation of autonomy that gets under my skin. The 'predator' character often operates on a logic of possession that completely overrides the other person's will. That creates this suffocating emotional conflict where the target is fighting two battles: one against the external threat, and a more insidious one against the part of themselves that might be responding to the intensity, the hyper-focus, or even a twisted sense of 'being chosen.' That internal war is where the real intensity lives.
I just finished a web novel where the male lead had this chilling, methodical obsession. He wasn't just passionate; he was rewriting her reality, isolating her, making his presence the only constant. Her conflict wasn't about love or hate, but about the erosion of her own mind. The obsession acted like a psychological trap, and her emotional turmoil came from trying to find a 'self' outside of his distorted reflection of her. It's less romance and more horror, but the emotional stakes feel terrifyingly high.
What makes it work is when the narrative doesn't glorify the obsession as mere passion, but truly sits in the discomfort of that power imbalance. The conflict isn't resolved by the predator 'winning,' but by the narrative forcing a reckoning with the damage done.