That question is very broad. There is no 1 strongest deck. Most people count Dark Armed Dragon and Monarch decks as the most powerfull. I have a Monarch deck and a DAD+Dark World deck. If your starting out, you probably want to use one of thoses. My favorite deck is my Sanctuary in the Sky deck. I have 5 different versions, each with dif goals (such as lock-down, power up, card draw, ect)