Guide to unlocking all Operators (Call of Duty: Modern Warfare)

There are a total of 21 different Operators in Call of Duty: Modern Warfare, and each operator can be used for multiplayer games. They all have different appearance and executions, but they don't have unique abilities like the Specialists from previous games (We've got Field Upgrades for this in Modern Warfare).

Below are all the 21 different Operators, as well as a guide to unlocking them. We have put them en categories sorted by what we need to unlock them, not by their groups.

Operators unlocked from playing the Campaign

Bale: Unlocked when completing the mission "Into the Furnace" on any difficulty.
Azur: Unlocked when completing the mission "Old Comrades" on any difficulty.

Yegot: Unlocked when completing the mission "Proxy War" on any difficulty.

Thorn: Unlocked when completing the mission "Piccadilly" on any difficulty.

Wyatt: Unlocked when completing the mission "The Wolf's Den" on any difficulty. 

D-Day: Unlocked when completing the mission "Hunting Party" on any difficulty.

Operators unlocked by getting kills with a certain weapon or a certain way in multiplayer mode

Minotaur: Unlocked by getting 300 kills with an Assault Rifle in multiplayer mode.
Grinch: Get a total of 100 headshots in multiplayer mode, with any weapon.
Kreuger: Get a total of 25 Finishing Moves in any multiplayer modes.
Charly: Unlocked when playing at least 25 different Public Matches.
Domino: Unlocked when you win 5 matches of Gunfight mode.
Raines: Get a total of 500 killes with any LMG weapon in multiplayker mode.

Operators unlocked from Spec Ops

Rodion: Complete "Operation: Just Reward" in Downtown Verdansk in Spec Ops mode.
Zane: Complete all the Co-op Operations in Verdansk.
Syd: Eliminate 5 Juggernauts in any Co-Op Operation.
Otter: Complete "Operation: Paladin" in Western Verdansk.
Golem: Complete "Operation: Headhunter" in Downtown Verdansk.
Alice: Complete "Operation: Harbringer" in Eastern Verdansk.

Operators unlocked from special means

War Pig: Unlocked by owning the Call of Duty: Modern Warfare Operator Pack.
Crew Expendable: Unlocked by owning the Call of Duty: Modern Warfare Operator Pack.
All Ghillied Up: Unlocked by owning the Call of Duty: Modern Warfare Operator Pack.