Mothra - Avatar of Defiance - is a flying trampler with a poison cloud. A5N4. It's a pity that you can't throw in a pair of fairy twins for good measure (but you probably will be able to in a patch or two, the internal code would definitely support it.)
For that matter, if the X%/turn chance of turning into another monster that the amulet of lycanthropy gives is ever available as a creature power, you could have baby mothras that grow up at some point.
Anyhoo, King Gidra cannot, unfortunately, have three head slots
. But he can have three poison bite attacks (the poison bite of the hydra), large amounts of earth and astral, AND three lightning bolt attacks, and he can be Avatar of Void.
The Avatar of Justice cannot be denied - he is Gamera! A3W3F5, and he's got a protection north of 30. Copystats on an abyssian to make him stronger in the heat.