Amuro Ray
White Unicorn is believed to be the legendary ace Amuro Ray, based on the physical appearance, personal logo, military ranking, Yurii's memory of their encounter at Side 6 during the One Year War, and most importantly, Toru Furuya being the character's voice actor. His Zeta Gundam unit appears to be the same one that Amuro piloted in the short CGI film "Green Divers" (white with purple stripes, plus Amuro's signature "A" symbol on the left shoulder armour).