I had a Wort, the Raidmother deck about 6 or so years ago. Managed to get all the right cards to produce an absurd amount of tokens without infinite mana. Made a bunch of tokens with Mana Echoes out and used it with Perilous Forays to fetch every land with a basic type one turn, and then the next turn I used Goblin Offensive, Saproling Symbiosis, and two Regrowth-type spells to recur them over and over with a Parallel Lives out. Ended up downloading a big number calculator app on my phone to do the math for me. By the time I was out of colored mana, the exponent was into the millions. Dropped a Goblin Bombardment and ended the game. Had I done the math and waited for the best time to tap Gaea's Cradle, the number could have been much higher.
WBG Karador, Ghost Chieftain
B Toshiro Umezawa
BG Pharika, God of Affliction - Necromancy and Politics
WWW The Church of Heliod
WBR Zurgo, Helmsmasher
RG Wort, the Raidmother
UBR Jeleva, Nephalia's Scourge
UG Vorel of the Hull Clade