Ok [the real] Clive, listen up because these orders are very complex. First, I want you to start off with a tactical Earth Power to land some good damage. The opening in the roof isn't all that big, so there shouldn't be much rain anyway. Start moving backward regardless. Now comes the tricky part: I want you to follow that up with another Earth Power. This should really unsteady him, and then he'll be brought down by a move slipped in just for variety: Earth Power!
So that all boils down to this:
Earth Power ~ Earth Power ~ Earth Power