At the very beginning of the fight, use the Line Launcher to kick into him. Now, the fight really starts, as Joker pulls out a pistol. Stay on the opposite side of the barrels, making sure to roll-dodge as Joker's reticle closes in on you. After three shots, Joker needs to reload; run up and punch him when he's distracted.
For the third phase, Joker will pull out an electrified baton and start charging maniacally at you. Stand in place as joker runs towards you, then line launch to the other side of the room at the last second. When you reach the other side, immediately line launch again to kick the Joker. The fourth and final phase combines the gun and shock stick, with an added twist: a timer, due to the poison gas that's filling the room. Simply use the same strategies depending on the Joker's weapon of choice, and he'll finally get knocked out of commission.