Krang

Commander Krang is an alien character from another dimension seeking to conquer ours who appears in Out of the Shadows as the true main antagonist where it is the first official live-action appearance of the character. He had sent three components of a machine to our dimension that, when united, would open up a portal to his dimension.

Biography
After Shredder escapes captivity by teleporting in the beginning of the movie, Krang teleported him to his dimension to tell Shredder about his plans for Earth. In particular, his transport device the Arc Capacitorwas splintered,and its parts scattered across the Earth years ago that had the capability to make a black hole connecting his dimension to Earth once reassembled. Krang requested that Shredder gather them so that he would be able to invade Earth and rule the world. He also gave Shredder a purple ooze capable of mutating humans.

Once Baxter Stockman assembled the Arc Capacitor, Krang emerges and immediately began assembling his war machine the Technodromehowever, Krang had no second thoughts about betraying Shredder, freezing him and locking him away with his collection of other defeated foes.

But the Ninja Turtles were able to intervene, confronting Krang aboard the still-assembling Technodrome, fighting him and his android body in the process. They locate the beacon around which the Technodrome is assembling and hurl it back through the portal, taking Krang and the rest of the Technodrome with it while while April, Casey, and Vernhelped reverse the Technodrome's components to return to Krang's dimension. Defeated and buried under his android, Krang swore that he would eventually return, stronger than before..

Trivia

 * Fred Armisen was originally going to voice the character, but scheduling conflicts made Armisen unavailable.
 * On Donnie's computer screen his name is spelled as "Krang." However in the credits, his name is spelled "Kraang".
 * Brad Garrett, who voices Krang in this film, is best friends with Pat Fraley, who voiced Krang in the 87' show. Fraley personally endorsed Garrett as Krang when he was announced.