Amal

Amal is Aladdin's best friend, but vanished when he and Aladdin were children.

Aladdin (TV series)
In truth, Amal had been seduced by the powers of a legion of monsters known as the El Katib, a.k.a. the Shadow-Walkers, but did not realize the price of the power he was given. Seven years later, Amal had fully transformed into a Shadow-Walker and during the three nights of the full moon sought out potential recruits. On the third night, Amal would find himself facing his old friend, Aladdin as he sought to recruit a boy named Wahid. After several skirmishes, Amal succeeded in recruiting Wahid and began the boy's transformation.

Wahid admitted to Aladdin his fall to the El Katib's offer, and by this, Aladdin realized the monster he'd been fighting was Amal. Amal cruelly confirmed his suspicions, maliciously stating, "I too have finally made something of myself... Aladdin!"

At that point, Aladdin's friends arrived, prompting Amal and Wahid to flee to the bottom of a well where Amal opened a portal through the shadows and they escaped through it. Genie however managed to catch the portal and keep it from closing, allowing him, Aladdin, Carpet, Iago, and Abu to follow the two to another location where Aladdin suddenly realized the El Katib had not started with Amal, that someone else was behind this. T'was revealed here that the mastermind behind the legion of the El Katib was Mirage.

Mirage obliged with Aladdin's demand to release the children who had been too afraid to fall for the Shadow-Walkers' offer, and that she herself had started the El Katib to gather a legion of minions, waiting every seven years to bring new blood into the kinship, that Amal had been a fine example and she had high hopes for young Wahid. Mirage then opened the portal into the Shadow Realm and told Wahid to enter. The boy refused and was horrified at the price of the power he'd been given: The El Katib can only walk the earth for three nights once every seven years, and he would be bound to serve Mirage forever, and if he didn't enter the Shadow Realm before the moon set, he'd die. Aladdin bargained with Mirage: Return Wahid to normal and she'd have Aladdin as her servant. She agreed but was tricked, and sicced the El Katib on Aladdin and his friends.

Amal caught Aladdin in his grasp, Mirage commanding him to kill Aladdin. Amal hesitated and then refused, stating, "He was my friend."

Enraged, Mirage prepared to kill Amal but stopped when she saw the moon was just about to set, and the portal close. She mockingly stated, "Then die, Amal die. Farewell!"

The moon set, the portal closed, and one by one the El Katib who hadn't made it to the portal began to fade from existence. Amal accepted his fate and said his good byes to Aladdin, but was astonished to see his monstrous arm revert to a human arm, perplexing them all but Genie reasoned that by refusing to kill his old friend, Amal was unworthy of being El Katib since they can't have any feelings to others.

Some time later, garbed in a cloak, Amal hugged Aladdin goodbye, stating that with every good deed he performed, he seemed to regain more and more of his humanity. Aladdin asked Amal to stay and do good in Agrabah but Amal declined, saying Agrabah had Aladdin to protect it and that there might be somewhere else Amal could be of help.

Shaking hands, Aladdin wished his best friend well and telling him, "You make something of yourself."

And with that, Amal walked off into the desert, but what happened to him afterwards remains unknown.

Personality
As a child, Amal stole gems for himself. Aladdin told him that it wasn't right, but Amal pointed out that Aladdin steals stuff too. Aladdin tells him that he steals food to eat. As El Katib, he was cruel as the others until he was told to kill Aladdin which he couldn't bring himself to do because Aladdin was his friend as a child.

By proving himself not a killer out of friendship, Amal lost his seed of evil. Desiring redemption, he chose to leave Agrabah to be of help to others, to, as Aladdin encouraged him, to make something of himself.

Powers
Amal, as El Katib, possesses several powers given to him by Mirage. He possesses phenomenal strength, the ability to deflect magic, teleporting through shadows, and he can scale walls like a gecko. He was also immortal but lost that power when he lost his seed of evil.

Whether or not he retains these powers after he leaves on his road to redemption is unknown.

Trivia

 * Amal's Shadow Walker appearance was very similar to the Imps, one of the enemies from MediEvil.