Loyalty

Mass Effect 2 features a Loyalty system, whereby completing a unique quest of personal importance for each squad member unlocks the character's fourth special ability as well as their alternate outfit. Loyalty additionally has an effect on the end game mission. Abilities unlocked through loyalty can also be learned by Commander Shepard using the Advanced Training research upgrade, though only one may be learned at any given time, and can also be accessed when creating a new Shepard or importing a Shepard from the original Mass Effect.

Accruing Loyalty
At any time after completing the Horizon mission, you will be informed by Kelly Chambers that that member would like to talk with you. The trigger for different loyalty missions is variable &mdash; some require exploring dialogue options, but all (except possibly for Legion's) can be triggered simply by the number of missions Shepard has completed. Completing this mission will cause that squad member to become loyal to you, enabling an alternate outfit, a bonus power, and improving their chances of survival during the suicide mission (provided you make the correct decisions during the mission). For some squad members, it is possible to make choices during their personal mission that will prevent their becoming loyal, even though the mission is considered complete. To engage a loyalty mission, the relevant character must be in your squad, with the exception of Samara, who shows up at the appropriate times (though it is, however, a good idea to bring her along).

You will acquire the 10 loyalty missions in the following order: Jacob, Miranda, Jack, Mordin, Grunt, Garrus, Samara, Tali, Thane, Legion.

If you do not recruit a squad member, and the previous loyalty mission comes up, such as you have Samara's and you haven't recruited Tali, then you will get Thane's instead. You will acquire Tali's after you complete an assignment or mission.

Zaeed Massani's and Kasumi Goto's loyalty missions are automatically available upon recruitment.

Confrontations
After completing their respective loyalty missions, two pairs of team members will end up in an argument:
 * Legion and Tali argue because Legion has scanned Tali's Omni-tool for information on the Flotilla and wants to transmit it back to the Geth fleet
 * Jack and Miranda argue about Cerberus' and the Illusive Man's responsibility for the experimentation on Jack

This will happen as soon as the Commander returns to the Normandy after finishing a loyalty mission, and Shepard will automatically be brought in to settle the dispute. Shepard can choose to support one squad member during the dispute, but the other will lose their loyalty as a result.

In order to placate both squad members, it is necessary to choose a Paragon or Renegade conversation option. If Shepard does not have enough Paragon or Renegade points, the options will be greyed out, forcing a choice between the two squad members. (There is disagreement whether an almost full Paragon/Renegade bar is required, or if the required points are scaled to Shepard's level and/or game progress. The safest solution is to save one of the pairs loyalty mission to near the end of the game, where one has accrued sufficient points to fill the Paragon/Renegade bar.)

It is possible to regain the lost loyalty of a squad member with another Paragon or Renegade test later. However, the team member whom Shepard does not support will no longer respond to romantic overtures, even if their loyalty is later regained. Losing the loyalty of one of the team members will not result in the loss of their respective special power, nor the Commander's access to it through the "Advanced Training" research project.

Loyalty Powers
Summary list of bonus powers unlocked after each loyalty mission is complete.
 * Armor Piercing Ammo (Garrus)
 * Barrier (Jacob)
 * Dominate (Morinth)
 * Energy Drain (Tali)
 * Flashbang Grenade (Kasumi)
 * Fortification (Grunt)
 * Geth Shield Boost (Legion)
 * Inferno Grenade (Zaeed)
 * Neural Shock (Mordin)
 * Reave (Samara)
 * Shredder Ammo (Thane)
 * Slam (Miranda)
 * Warp Ammo (Jack)