Celadon City from Erika. Saffron City from Sabrina. Fushia City from Koga. Cinnabar Isalnd from Blaine and Viridian City from Giovanni. The Diamond Badge is used in the Live show.
Diamonds are the hardest substance on earth and the diamond badge is the hardest to win.
Giovanni uses it to lure Ash to his headquarters to try to take over the world. The Diamond badge cannot be found in the Pokemon game only in the live show. Mech Mew2 can only be defeated by Mew2. He uses the love Pokemon and his family from Ash to defeat Mecha Mew 2. There are however many good Pokemon sites to be found use your search engine to find them.