A good character that was brainwashed into doing evil against his will. Between putting his true self and an evil self he didn’t want to be, they chose the evil. They did this to so many characters. Why.
What do you mean so many. They did it with Marik (his better half barely dueled except through Joey and Strings). Yami Marik was the more iconic of the two character and fit into the setting. Zane does not really count as a dark side, something he himselfed acknowledge during his duel with Atticus. Sartorius and Yubel are best known for the appearance they used.