The True All-Star Battle is the twenty-first and last co-op event in Super Smash Bros. Brawl. In this event, you have to KO the entire playable cast of Brawl.
Strategies
If someone were unable to find an effective strategy to complete this event, they will more than likely find plenty of videos explaining other players' methods of achieving victory. Since the opponents seem to be more easily KO'ed than normal (as if someone had increased the damage ratio), most people find it useful to rely on characters with powerful one hit moves that can be used in over and over again without leaving themselves open to attack. Also, it will be found useful that since most characters come from the middle of Battlefield's top platform, you should stay there to Star KO the majority of opponents. One player should stay on the main platform in case any do not get Star-KO'ed. This is most useful when using a powerful character (e.g. Bowser) on the top platform and a mid-to-speedy character (e.g. Captain Falcon on bottom.
Pikachu and Pikachu
More than likely, using two Pikachus to make the most out of its down special, Thunder is one of the more effective tactics. Simply position the two Pikachus on the top platform and rapidly use Thunder. When used in this location, it will more than likely hit the opponents as soon as they enter the stage. It should make an instant KO
Snake and Snake
This tactic is similar to the one involving Pikachu, but instead makes use of Snake's Powerful upsmash. By only charging it halfway, you have enough power to instantly KO most opponents, and can perform it quickly enough to be used without fear of attack from the enemy.
Ike
This tactic involves standing on the uppermost platform and using Ike's up+A nonstop. The opponents will appear directly above you and get hit by the attack. Ike's up+A has high power and knockback which will cause a OHKO.
Link
Use his Up Smash to KO opponents with ease after being hit once twice or three times.
Sonic and Captain Falcon
This tactic involves weakening/accumulating damage with Sonic's Spin attacks, then grabbing the foe to Falcon Punch them for the knockout. Sonic should concentrate on one foe, while Falcon protect him until the target is around the 40-60% for the Falcon Punch. If outmuscled, Sonic and Falcon have enough speed to dodge the enemies. However, Raptor Boost should have enough knockback to KO.
Meta Knight and Meta Knight
This is probably the easiest--yet longest--way to beat this event. Both players should face inward on the middle platform and hold A. Enemies will drop into the storm of sword slashes and will accumulate damage almost endlessly. When their percentage reaches about 50, a speedy Dsmash (or, indeed, almost any quick attack with significant knockback) will instantly KO them. Repeat this process until all enemies are beaten. Another strategy is to catch them in a shuttle loop. It has a high chance of a 1HKO
Kirby
This is a fairly quick and easy way to beat the event, especially in easy mode. Choose Kirby for at least one player. Then jump to the top middle platform where the enemies begin spawning. When the enemy falls, jump above them and use Kirby's Stone attack. this will KO them instantly. Repeat as necessary.
Zero Suit Samus & Pikachu
As Zero Suit Samus, use her Laser Wire attack (Up B) to build up the foe's damage. When the foe's been damaged enough, Pikachu can use Thunder to KO them instantly.