Txt - autotune and that they aren't close. And that they're PrIviLegeD.
Bp - They didn't deserve their success. Youtube views too, though that's died out. Oh, and a host of other scandal specific bashing that somehow involves slut shaming, misogyny and overall nastiness.
exo - Rappers, don't sing live, aren't close (mess of a fanbase)
bigbang - scandals. Some of it's deserved.
Side note on the exo aren't close thing: I absolutely detest when people find a reason to bring up the lawsuit line into that. Mistreatment from a company, and subsequently deciding that the xenophobia is enough, shouldn't have ANYTHING to do with how close members are. If they aren't close now, it's because they probably haven't talked as life has taken them seperate paths. I suppose you could bring up that they had a messy breakup, but just saying "oh and a bunch of them left" is annoying. And happens way too much.