If he had the traditional lava attacks that could fit in with your suggestion of the ones that retain heat by having it left somewhere in the middle of his solidifying cool for awesome durability to staying liquid hot. The still hot version yet in solid form would have great durability despite loosing some durability.

Of course I'll have to also mention his superhuman physical enhancements. Given the true form he'll end up becoming he'd be able to demolish that little mech of yours in an instant. Mwahahahaha!