Dir En Grey - I hated them, I didn't know why they are so popular at all, I hated the screams, the music sounded uninteresting to me... (I think I've listened to them before I discovered mucc - with them I started to like screams) but then I don't know why I listened Ryouyoku no ame (I found out I'm kinda possessed with a word "ame" so that's why I guess). And I was like ah that's awesome! And I fallen in love with the screams and music! -still in a phase of discovering though-
almost the same goes for System of a down (I just listened to bad songs ) and Maximum the hormone (here I wathed Death note once more time and found out the ending is kinda crazy and awesome in the same time, but I still don't get why they're so popular )
And there're also some artists like this:
I downloaded some album and my feelings from it: "It's not that bad that I have to delete it but not that good I want to listen to it on purpose.." but then, after some time, I found out I love them for example 9GOATS BLACK OUT
or there are also some artists I still hate/don't like - Matenrou opera (I'm lazy to delete them I guess) or Devil Kitty they're horrible to me but the vocalist has so interesting voice (only voice I don't think he can sing) that I just don't want to delete them = that's only my personal opinion so sorry if you love them