"Leave them alone. They're insignificant, I'm only interested in warriors brave enough to fight." - The Supreme King
The Supreme King (voiced by Matthew Charles) is Jaden's evil side that once took control of him in the alternate dimension when he was looking for Jesse Anderson. After Jaden's painful duel with Brron, when Chazz, Hassleberry, Atticus, and Alexis were sent to the stars, the anger in Jaden went out of control, and the Supreme King took control of Jaden as his puppet. He duels with Elemental Heroes and Evil Heroes, he creates The Evil Heroes with a spell called Dark Fusion, and another called Dark Calling. His Ultimate fusion card is Super Polymerization, which can fuse monsters from both sides of the playing field. His goal was to rule the dimension with an iron fist. Jim tried to save Jaden from the Supreme King's control with the Eye of Orichalcum, but he failed and was sent to the stars too. But the King was defeated when Axel Brodie dueled him, and it resulted in a tie. When Jaden came to, he felt guilt driven over what he did as the Supreme King, but he eventually was able to use the power of the Supreme King to duel Yubel.
- In Jeffrey, Jaden & Friends' Adventures of Indiana Jones and The Temple of Doom, Jaden sacrificed himself to Set and the villains, in order to save Alexis' life. Set turned him back into the Supreme King, but the heroes were able to weaken his control over Jaden with memories, because they didn't want to hurt him. While bringing Jaden back, Jeffrey personally spoke with The Supreme King himself, asking why would he want to help the bad guys. Alexis' kiss of true love brought Jaden back, thus killing the Supreme King once and for all.
- The Supreme King will be reborn after a small amount of Jaden's energy is taken by Kurata and given to Lucifer, so he can create a separate personality and be named Nedaj. Nedaj is Jaden spelled backwards. Nedaj would eventually begin to deteriorate, and use both negative energies of Jaden and Aichi to become a new person with no side effect, reborn as Aiden Yudou, and a villain in Aaron's Adventures. Aiden will eventually transform into a more darker version of himself and more legendary as well.
- In Japan, The Supreme King is Haou Judai, which translates into The Supreme King Judai.