Captain Barbossa is a non-playable story antagonist in LEGO Pirates of the Caribbean: The Video Game on all platforms, including Wii. He appears in cutscenes and as an enemy/boss, but cannot be unlocked for free play.
Traveler's Tales typically reserves major villains for boss encounters only. Barbossa's role as a recurring antagonist across the films makes him a narrative foil, not a playable hero.
Enjoy the 70+ other characters—the game has one of the largest LEGO rosters!