Is there a worst group of villains than...
...the Espada in Bleach?
Seriously, these guys are dropping off like flies, especially that one that Byakuya just recently took down. Not to mention they're all so stale and boring in terms of character depth and personality as well.
So far, only Grimmjow and the doctor seem to be the only ones worth while (at least the doctor losing to Mayuri was due to one-sided prep).
And let's not get started on the Arrancars that were easily wiped out by Hitsugaya and his gang.
I don't think I can think of any other group of villains that have been more disappointing, though I guess the Akatsuki aren't too far behind.