TOP 10: most memorable evil organization of the games

Well as you can without Abstergo)
GCD (C&C3).
Cerberus (Mass effect 2-3).

Majestic-12 from the first Deus ex,mrazota are truly the most unscrupulous and cruel organization is ready to do anything for the seizure of power

Something I do not remember anything except the Umbrella Corporation from Resident Evil.

1)Enclave - Fallout 2
2) Umbrella Corporation - RE series
3) Alliance - Half-Life 2

Umbrella Corporation from Resident Evil
Cerberus from Mass Effect
Abstergo (aka the Templars) from Assasins Creed
The mythic dawn from The Elder Scrolls 4 Oblivion

LodedDоrmoUse
Well, I remember them more) Well its not their players and that's for sure.

Dark brotherhood - The Elden Scrolls
Salamandra - The Witcher
Triad - Sleeping Dogs

1) NOD - Comand&Conquer 3
2)The Knights Templar Assasins Creed

Termibus
Ie the Nazis in the metro, you never confused? Red means worse?

Something all around go...
GLA - Generals
Yuri Red Alert 2
Penguins Starbound :D
CIS, Empire - Star wars

Dark_Link
It's how you look... Yes. Intentions are not quite evil, just what resulted? Umbrella of RE, in fact, a twin brother UAC, even a fluffy to be. Those, too, originally to do scientific research. Produced medicine and food.
If you look at any of these organizations, they too have a meaning in their actions.
Enclave Fallouta wanted to cleanse the wasteland from the effects of radiation, mutants and anarchy, and to restore governance. Not such a bad goal initially.
Cerberus in Mass Effect I tried to achieve more rights of humanity in the galactic organizations. Them the main purpose is to fight for humanity's survival and strengthen its position in the Galaxy.
So, the organization becomes evil not because of the fact that since its inception, wants to destroy the entire universe (I doubt that such exist), and for the consequences of its activities. UAC and in the end clearly not white and fluffy. 've done a lot of...

Dominion StarCraft.

Ubmrella(Resident Evil).
The Combine(Half-Life).
Abstergo(Assasin's Creed).
Salamanders(The Witcher).

S. T. A. L. K. E. R - Monolith
Saints Row 3 - Syndicate
Borderlands 2 - Hyperion

The Alliance of Half-Life 2
The enclave Il Fallout 3

1. The Alliance Of Half-Life 2
2. Cerberus - Mass Effect
3. Abstergo - Assassin's Creed

1. The Alliance of Half-life
2. Blackwatch - Overwatch
3. The army of undead - WoW
4. Cerberus - Mass Effect

1. Enclave - Fallout
2. The Aldmeri Dominion - The Elder Scrolls
3. Ultor In Red Faction

the Witcher 3

Umbrella Corporation