Rako is a Cambodian assassin.
Rako is an imposing figure, standing 7 feet tall. He has a long face and black hair.
He wears a suit of armor evoking that of a samurai, and consists mostly of black plates, each lined with gold. He wears a helmet with a red visor, and a red sash around his waist.
Rako was raised by
General Trang, but as he grew up, he went his own way. He became an assassin armed with a deadly sword, and worked for  Alec Rois.
Rako assassinated all people involved in the trial of
Nathaniel Adams, starting with Shirley Mason in her Arlington home.
His next victim was his former caretaker, General Trang, but
the Team intervened before he could kill him. After a short fight, he did succeed, and escaped. 
Henry Yarrow and Alec Rois at an old airbase to ambush the Team. Rako was taken out by Aqualad, who suffocated him with a bubble of water in his face.
Shuriken: one of Rako's preferred weapons, four-spiked throwing stars. 
Sword: Rako's sword can cut through anything—even Superboy—because it has been forged by the X-Ionizer. It gives off a blue gleam.  Helmet: Rako's helmet has a visor that allows him to see infrared. 
Rako is based on the Captain Atom villain "The Cambodian", who, like Rako, murdered several people involved in Nathaniel Adam's court-martial. However, in the comics, the Cambodian was an adult during the war (since the stories took place in the late 1980s) and lead the ambush at Hill 409.
Due to the political incorrectness of "The Cambodian" name—which had always made Weisman uncomfortable—the name was dropped in favor of the character's real name, Rako. Rako was redesigned by Christopher Jones, based on original artwork from the Captain Atom comic book. 
Weisman, Greg (2016-12-13). Question #21675. Ask Greg. Retrieved 2016-12-13.
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Weisman, Greg, Kevin Hopps (w). Jones, Christopher, Carrie Strachan (p). Davis, Dan (i). Atkinson, Zac (col). Sienty, Dezi (let). Chadwick, Jim (ed). " Hot Case" Young Justice 10 (November 16, 2011), New York, NY: DC Comics
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Hopps, Kevin, Greg Weisman (w). Davis, Dan, Christopher Jones (p). Davis, Dan (i). Atkinson, Zac (col). Sienty, Dezi (let). Chadwick, Jim (ed). " Cold Case" Young Justice 9 (October 19, 2011), New York, NY: DC Comics
Jones, Christopher. Character Design: The Cambodian. christopherjonesart.com. Retrieved 2012-01-09.