Advance Wars/COs

Andy

 * CO Power: "Hyper Repair", increases all units' HP up by 2
 * Unlocked by: Default

Andy has all-around average units.

Max

 * CO Power: "Max Power", direct fire units get 25% offensive bonus and 1 extra square of movement
 * Unlocked by: Default

Max is a direct fire specialist, all of his direct fire units get a 50% offensive bonus. Max's indirect units get a 10% offensive reduction, and one less square in their range.

Sami

 * CO Power: "Double Time", infantry units get 30% offensive bonus, 20% defensive bonus, and 1 extra square of movement and lack moving penalties for that turn
 * Unlocked by: Default

Sami is an infantry specialist, all infantry units (infantry and mech) get a 20% offensive bonus and a 10% defensive bonus. Sami's troops capture buildings at 150% faster than normal.

Olaf

 * CO Power: "Blizzard", causes a snow storm for one day, which lowers the enemies' movement range
 * Unlocked by: Default

Grit

 * CO Power: "Snipe Attack", indirect units get 65% offensive bonus, and 2 range enhancements
 * Unlocked by: Winning the mission "Max Strikes!" with Max

Grit's indirect fire units get 1 bonus range, his direct fire units have a 20% offensive deduction.

Eagle

 * CO Power: "Lightning Strike", all units gain an extra turn, except for infantry
 * Unlocked by: Win all Green Earth missions using Sami

Eagle's air units require less fuel to move, and have 10% bonus to both offense and defense. His sea units receive a 10% deduction to both offense and defense.

Drake

 * CO Power: "Tsunami", damages all enemy units by 1 HP, unless they were already at 1 HP
 * Unlocked by: Win all Green Earth missions using Andy

Drake gets a 20% bonus of offense and defense to his sea units, and 20% deduction of offense and defense to his air units. It also rains more often when Drake is used in a match.

Kanbei

 * CO Power: "Morale Boost", troops receive a 20% offense and defense bonus
 * Unlocked by: Beat Kanbei's three missions in 8 days, 10 days then 12 days in that order

All of Kanbei's units have a 20% bonus to offense and defense, but cost 20% more.

Sonja

 * CO Power: Increases line of sight
 * Unlocked by: Beat Kanbei's three missions in 8 days, 10 days then 12 days in that order, and then win the 3 hidden missions against Sonja

Sonja's units have a longer field of vision and their HP are invisible to the enemy. All of her units are "unlucky" and 10-20% less effective.

Sturm

 * CO Power: "Meteor Strike" Sends a meteor crashing into the area with the highest concentration of enemy troops, damaging by up to 4 HP
 * Unlocked by: Unlocking every other CO

All of Sturm's units have a 20% offensive bonus, and a 20% defensive reduction. Terrain penalties do not apply to the movement of Sturm's units, except for weather.

Nell

 * CO Power:
 * Unlocked by: Finish the advance campaign