Niceee.
From Pokemo series:
Team Rocket
Team Aqua
Team Magma
Team Galaxy
Team Plasma
From Umineko no Naku Koro Ni:
Mariage Sorciere
The Witch Hunt
Chiester Sisters Imperial Guard Corp
Eiserne Jungfrau, the 7th District Repentance Agency of the Great Court of Heaven
SSVD, the 8th District Repentance Agency of the Great Court of Heaven
Queen's Knights (Suikoden V)
Secret Alliance for the Protection of Pretty Hunks in Real Endangerment (SAPPHIRE) (Suikoden V)
Howling Voice Guild (Suikoden series)
Japanese Task Force (Death Note)
Death Eaters (Harry Potter series)
Order of Phoenix (Harry Potter series)
Society for the Promotion of Elvish Welfare (Harry Potter series)
Hogwarts Faculty & Staff (Harry Potter series)
Anbu (Naruto)
Tantalus Theater Trope (Final Fantasy IX)
Specialized Extracurricular Execute Sector (S.E.E.S.) (Persona 3)
Fire Bringer (Suikoden 3)
Dunan Army (Suikoden 2)
Liberation Army (Suikoden)
Ala Rubra (Mahou Sensei Negima)
Ala Alba (Mahou Sensei Negima)
Cosmo Entelecheia (Mahou Sensei Negima)
Organization XIII (Kingdom Hearts series)
S.T.A.R.S. (Resident Evil series)
I hope they count.
--
Oh, I am one yet many.