Genie Jafar

Genie Jafar is a form of Jafar that the character becomes at the end of Aladdin.

Aladdin
Jafar uses his final wish to become "an all-powerful genie", but is then surprised when Aladdin reminds him that genies are not free entities as he is sucked into his new black lamp, dragging Iago with him. Genie flicks the lamp into the Cave of Wonders.

The Return of Jafar
Then, in The Return of Jafar, Iago escapes their lamp and defects to the good guys. Aladdin, Jasmine, the Genie, Abu and Carpet engage Jafar in combat, but even when bound by the rules of the Genie, he easily outmatches them, using his tremendous powers to stop them from getting the lamp. His indiscriminate use of power opens a fissure in the ground which is filled with magma. Thoroughly trapped, Aladdin, Jasmine, the Genie, and Abu face certain death when suddenly Iago reappears and grabs the lamp. Jafar blasts him, leaving him for dead, but Iago manages to recover for a moment and uses his last ounce of strength to kick the lamp into the magma. The lamp melts upon landing in the magma, and thus Jafar meets his end by violently imploding into a cloud of dust.

Kingdom Hearts
Having assumed the form of a gigantic genie, Jafar picks up massive fireballs to throw at the party. You can do damage with your new Blizzara spell, but your best bet is to aim for the lamp, which Iago carries around the room. Lock onto the lamp and follow Iago to smash it repeatedly. To avoid damage from Jafar’s fireball attacks, use Dodge Roll, and cast Aero on your other party members (since they can’t dodge as well). Alternatively, you may use Guard to fend off the fireball attacks. For winning this battle, your Fire magic is upgraded to Fira, and you can read the first Ansem’s Report.

Kingdom Hearts: Chain of Memories
Jafar does about the same moves as he does in Kingdom Hearts, but with more time in between attacks. Just as in the first game, attacking Jafar will not deal any damage: you have to hit Iago, who is carrying the lamp. As you cannot use Guard in this battle, it is best to Dodge Roll away from his fireballs, or break Jafar's cards. Keep your Sleights for the lamp. Like all other boss battles, heal when necessary. In Reverse/Rebirth, keep the King Mickey card as the third card for a sleight if your HP is running low and you cannot break Jafar's attacks. Also, the Maleficent enemy card helps a ton since it boosts Riku's strength without slowing down his reload speed (since Riku can reload his cards instantly).

Kingdom Hearts II
This time, the battlefield is the sky of Agrabah. You have the entire field to exploit to your advantage. However, you might be left at a disadvantage because you fight Jafar while flying around on the Carpet, and this might create some maneuverability issues. Also, beware of the buildings/debris that encircle Jafar - they deal substantial damage to Sora.

Jafar has several attacks in this battle, namely a fist swing, fireballs, lightning bolts (In which he says "Cham Dabadabada"), pillars (only when he has the hand aura), and capturing Sora, making him unable to move (and invincible to the fist swing). All of these attacks can be guarded with Reflect magic.

Unlike previous battles against Jafar, you now attack him directly instead of attacking his lamp. Jafar has two weak points, notably the head and the torso. Depleting Jafar's torso health will leave him stunned and activate a Reaction Command that will allow Sora to tie Jafar's body parts together and stun him even longer. You can also attack his hands, but it is quite dangerous.

Every now and then (usually when he snares Sora) Jafar will shift Sora to another dimension (just as Zexion does in the Data Rematch). Debris will be flung against Sora and if Sora does not guard himself against it, his HP will be greatly reduced. This can be avoided, however, by flying around (mainly in circles as well as up and down) constantly. You will get hit, but not as much as you would by staying where you are.

Use physical attacks as much as you can, and heal when necessary.

Kingdom Hearts coded
You must fight Jafar after entering the keyhole in Episode 5 of Kingdom Hearts coded. Iago is also present during the fight and holds Jafar's lamp.