The first time you complete one of your squadmates' loyalty missions, they'll receive access to their fourth power. At that point, you'll be able to train in that power as well, either in that game (by visiting the upgrade terminal) or by starting a new Shepard. Each power must be unlocked by completing each character's loyalty. In normal, unmodded gameplay, those missions will start to become available about 1/3-1/2 of the way through the game, after the Horizon story event, though if you have the Kasumi & Zaeed DLCs you can get theirs out of the way as soon as you recruit them.
(There's also Stasis, which you unlock simply by completing Lair of the Shadow Broker, since that's sort of Liara's loyalty mission. It's bugged, however, and won't show up for new Shepards, you have to wait to get to the Normandy and train it there.)
Oh, and soldiers are the one class that needs a bonus power the absolute least. Most of them will just get in the way. I like 1pt Neural Shock, and some folks have success with Flashbang Grenade. AP Ammo can be nice in the early game when you haven't unlocked Incendiary yet but once you can level that up you should train out.
Modifié par Quething, 10 septembre 2011 - 01:04 .