Mostly "toxic" relationships or "obbsesive affection (in the good "I will destroy everything for you" way) and primarly that of a romantic nature....idealy the FL has the upper hand.

Also novels where the ML's burning affection is not reciprocated by the FL. This can be changed as the plot evolves, or until the end the love won't be reciprocated.

Fantastic realm/ Royalty/Modern world/Ancient times - doesn't matter as long as the FL is not treated miserably, even if there is angst, mixed emotions, bursts of anger, sad and tense moments. The ML lead definitely can not be a total scum and the FL a weak, emotional damsel.