Trinity Armor

Trinity Armor (トリニティアーマー), is a giant robotic Unverse fought in Radiant Garden made out of three individual parts like the Guard Armor Heartless. Trinity Armor is the only known boss to fight against Terra, Ventus and Aqua at the same time.

Video
The battle with Trinity Armor is similar to when Sora was facing Guard Armor with Donald and Goofy. The battle style of Trinity Armor is the same to Guard Armor since when you destroy a piece you have get the other one. http://www.youtube.com/watch?v=G5Csfnm70-U