Wasn’t that meteor eruption 🌋
Well I definitely remember him doing a massive aerial aoe attack of some kind where he rained fists on his enemies.
Honestly though, a more precise attack like a minigun could work. He could fire off sharp volcanic rocks and ash with high force like Ultimate Humungousaur in the gif above.
He could also use an axe if he can harden his body into rock, like the Sharpened Volcano Fragment...
...well hopefully stronger than that.
But really, considering that Kuzan and Kizaru both had swords, a magma blade is very likely.
Since a broad blade was what you mentioned, we could have an executioner's sword instead of an axe.