Oh my gosh, I have so many, but I'll try to limit a bit. :X
Hikaru Utada - One of the biggest disappointments of my music life. It all started with ULTRA BLUE. I had the biggest hope for that album, but except for COLORS, BLUE, and maybe one more, the album was pretty ******. And HEART STATION was even worse. And then This Is The One was a little better, in my opinion, but still pretty bad, and kind of a sell out.
MUCC - They were an amazing rock band, and one of the few that stayed true to what Visual-Kei really is...... And now they're like L'arc~en~Ciel junior. **** that!
I still love their old stuff sooo much though.
Ai Otsuka - She used to be freaking amazing, lol!! She had her ups and downs in the music, but I was always impressed with every album, until LOVE LETTER... My gawd, that is a terribly boring album.
Don't like the style she's had lately, either... I still like her a whole lot, but her actual music has been a huge disappointment to me for a while.
Chihiro Onitsuka - This is another person who's older music I still love, and I don't have anything against her, I just hated her last album, and LAS VEGAS wasn't too good, for me, either. :\ I also hate that she is VERY limited in variety...
Do As Infinity - There was a time when I loved them. But now, no. ETERNAL FLAME was pathetic, with the exception of Meramera. Considering that, plus the fact that they were supposedly broken up before that, I just don't care anymore if they don't release anything again. I mean, I thought that's how it was gonna be before, anyhow, hah.
sweetbox - Jade is truly what made this band. The girls before her didn't bring anything amazing, and the new girl can't even try to bring 1/100 of what Jade did. So, along with Jade and Geo, I left sweetbox, and I am currently following their various projects outside of the band.
Aya Kamiki - I had a lot of hope for her. One of the few current acts who did real, regular rock. But most of her past works were sooooo...well, below average, at best, for most of the stuff. And her image and everything is starting to go somewhere else, completely, with avex, it seems. That's a real disappointment, there--I was hoping avex would really boost her up in a positive way.
Whatever. I'm done expecting anything from her, and I'll just focus on the songs that I do love, and her old, true rock style that she seems to have lost with the label change.