Not very original but I love yanderes (especially when they're older brothers lmao)! I really like angst, and I love seeing an LI acting all desperate and crazy about the MC ;)
I believe it can explore some interesting dynamics and developments, like dealing with whether the LI is truly in love with the MC or if it's just some type of attachment towards her. If the MC was previously in love with him but and gets scared when she learns about his yandere tendencies, it introduces all kinds of angsty and depressing sides to their relationship, like feeling that she was deceived by the LI the whole time! And of course, the more possessive scenes are very fun to read! Haha
An older brother yandere is even better, as it shows his increasingly unhinged behavior being either because of the forbidden nature of his love towards the MC, or some sort of toxic codependency he developed with her! All sorts of deliciously messy dynamics... I love the drama lmao
As for one I dislike (though I wouldn't say I hate it), kuudere. Not a surprise at all, since I love messy and desperate characters, it makes sense that closed off LIs are not my type lol
Many games take their sweet time actually getting the kuudere to open up and be honest about their feelings ;b
I have been pleasantly surprised by some kuudere characters before though, so it's more a slight distaste than full on dislike for them!