Actually... Wondertomb, as many people refer to it, is actually pretty easy to kill, with something like a charizard. This is because of the Game's coding system. Seeing as there is only one pokemon in the series that has wonder guard - Shedinja - that's the part of the code that the game recognises.
Put simply, if you have a wondertomb - unless you're the shizzle when it come to hacking - then the game will recognise it as a Shedinja, not a Spiritomb - due to the fact that Shedinja is the only pokemon with the wonder guard 'code' - and as we all know, bugs are weak to fire, flying e.t.c., plus it's also part ghost type, so it's weak to ghost as well!
