While playing the game in any mode, press Start, go to "Settings", and select "Game Settings". When the screen appears at the top, one will be marked "Global Slides". Press R2 until it gets to "User Slides". Set everything on that list to 100. Continue your game and your team should be unbeatable.
First, turn off all the rules. Then, take a good dunker (for example, LeBron James) and run down the baseline until you get under the net, then pop out and press Square. The dunk will be unblockable, and if it is done correctly it will always go in