1- Well, Ditto is by far, the BCIF. Put 4 of him in a deck with 54 energies, 1 Wynaut and an E-Belt and you have the BDIF.
2- Ditto is the metagame. Nothing beats ditto. Ditto is the rock paper and scissors without the weakensses.
3-Ditto is a combo paradox. He needs nothing else to win...