The free Smack Boxing Lite features 3 opponents and is playable on the "easy" difficulty level. The premium version offers 8 unlockable characters and 4 levels of difficulty, easy, medium, hard and insane.
Otherwise Smack Boxing Lite is fully featured.
About Smack Boxing:
With the usual twist of sarcastic humor we revamped the iPhone multitouch controls into the best stress relief experience ever! Boxing has never been this fun before. If you liked NES Punch-Out, then this is the right game for you!Swipe, tap and tilt to perform a multitude of different boxing moves including jabs, uppercuts, hooks, sidesteps and blocks to unlock new opponents and levels of difficulty.
iTunes links: Smack Boxing
Smack Boxing Lite