For all of its popularity amongst the younger generation, I hate Team Galactic. Their underlings come off as much stupider than Rocket's underlings, and their admins, while legitimately evil, seem so out-of-place in a Pokemon game. o_0
...all their effort to summon a legendary pokemon that I usually just kill in my games (of course, this can be a fault for Aqua/Magma as well, but Groudon and Kyogre are infinitely more badass than Dialga and Palkia).