I always felt like Charblecher was the fastest, win or lose. It's either Turn 1 win, or Turn 1 loss with that deck. Unless you meant good decks.
Belcher is actually the type of deck that sometimes wins long games. Playing out petals and walls while drawing into a couple red blasts and rituals to beat soft counters is more effective than it should be. Helps that people aggressively mulligan to force which might leave them with nothing after they stop your first attempt.