[@thewizardguy]
Destructive power =/= Strength of the attack.

Swords have virtually no range. Even if Luka hit a mountain with his sword, it wouldn't destroy the entire mountain, because that's not how swords work. If he distributed the force of his swing across the entire radius of the mountain, the mountain would be destroyed. If you were a regular sized guy covered in miniature mountains, each with the durability of an entire mountain, he would be able to break through with his sword.

It's the same with all of his abilities. He's not an anti-mountain specialist with special explosive beam swords. He's a single combat specialist, and that's it. He just happens to come from a world where there are little girls with the durability of mountains, that he needs to be able to hurt.

And yeah, he can only use a weak version of Sword of the Heavens. It's Micaela's technique, after all. I was talking about its complete form when I compared it to Quadruple Giga.