For his second form, he's weak to Web Spider's weapon.
He starts the battle by throwing his scythe in a circular pattern in front of him. You can hop on a wall to avoid that. Then, he'll throw it at you. If it lands on the ground, it'll generate lightning on the ground in both directions. Furthermore, he'll send homing missiles at you. Therefore, try to have the scythe land on the wall. This will generate electricity vertically on the wall, but you should have enough time to wall-kick and dash off the wall and get behind him. He'll be shooting lasers from his eyes and be completely vulnerable.
Rinse and repeat. I'm confident you can do it. ^^