I can't stand the mainstream-commercial music. It has nothing to do with the artistic process that envolves create a song. (for ie: MJ was mainstream in the 80/90 but his music was real, full of emotion and music-sense)
Specifically i hate the music full of auto-tune, did with a computer loop system (even FL works for this) and with a big-bobbed/juicy ass girl or a gay-looking guy as an image to earn fast and easy money.
About Grindcore xD, I had a grindcore band years ago, was called Mazakratula (in spanish, is something like... "massacre-penis") but I don't listen Grind. I take this genre of music as a non-serious thing, the lyrics are ridiculous and the music is almost just noise lol. But anyway, it's fun to watch and play (although your ears could be bleeding in a one minute grindcore session).