When you think of ship-busters, you should really look at the Pacific, as the Navy planes were doing one hell of a job doing that. I would say the TBF/TM Avenger. It was designed to carry torpedoes and bust ships.
There was also a B-25 that was developed in New Zealand by Pappy Gunn and Jack Fox that carried a 75mm cannon on board. That must have been one heck of a jolt when that gun fired! I will have to see if I can dig out the story of it's first use. Three of them attacked some Japanese warships and before the Japanese knew what hit them, a battleship was down.