You can't.
Not available on Brawl, and never will be. Sorry.
Mewtwo was not included in Super Smash Bros Brawl, so you can't unlock or play as him in the game.
Mewtwo is not in brawl so that means you can't unlock him.
No mewtwo is not in the game super smash bros. brawl
mewtwo is not in super smash bros. brawl however mew is a trophy character
You can't get him in brawl.
Mewtwo is only in Super Smash Bros. Melee. He is not in Brawl
You can't. Mewtwo is only in Super Smash Bros. Melee.
Mewtwo and Roy are included as DLC in Super Smash Bros. for Nintendo 3DS/Super Smash Bros. for Wii U. Mewtwo and Roy are already in the game in Super Smash Bros. Ultimate. Mewtwo and Roy are not in Super Smash Bros. Brawl but are in Melee.
No.
You can't. Mewtwo only appears in Super Smash Bros. Melee.