Mostly "toxic" relationships and primarly that of a romantic nature.

Although the ML's are usually the one described of such acting, the FL's can be too.

Ussually the FL has the upper hand and the ML is a puppy, this also being the preference, but there can be exceptions in the list.

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. This being said, I gladly accept new suggestions that match this genre.