With the power of darkness enveloping the other law powers, it was easy to bind the different powers together.
However, that was just putting the powers together. To completely fuse them was much harder and increasingly challenging with each additional law power added to the mix.
Furthermore, some powers mixed well while others conflicted and made fusion far more difficult.
Nevertheless, Leon continued to test the limits of his abilities and power output. He proceeded to add the lightning power to the mix.
Lightning and fire had always produced great destructiveness. Even so, the result still exceeded his expectation.
After fusing lightning power with fire, solar, and dark powers, Leon was able to produce an attack on the same level as the very peak of Mid Paragon, just a bit short of reaching the power of Late Paragons.