It's big and heavier than it looks, so it's pretty powerful. But the special ability is if you charge it with power of existence and hit something indirectly (like if it's blocked), the attack will go through as if it wasn't blocked at all.
The incest twins used the sword against Shana and almost killed her; they're weak Tomogara without much power of existence. The size of the damage slash inflicted by the special ability is dependent on how much power you put into it.
So imagine what happens if Yuuji, with the Reiji Maigo (unlimited power) uses that sword. He could split anything, cities, mountains, even continents.