First, beat story mode. Then beat single player mode with almost every character. What I did was keep playing against my little brother. Then I went in Survival Mode with Sasuke and got 14 straight wins(i know, thats pretty bad but I didn't have Sasuke mastered at the time) Then I unlocked all the other characters.

This is something me and my friend have play-tested, tried out, and mastered in the game. When using Sasuke, we realize he has the potential to deal as much damage as a fully charged Chidori except without a fully charged one. (Though this takes as much chakra) By using this technique I have managed to beat all missions with Sasuke, won the Time Attack and had a record of 40+ in Survival (The game is in my friend's house thus I do not know, the first is his record of Itachi with over 50)

The combo is done best with full chakra and your opponent has no chakra (or at least, no chakra to do a Kawarimi (subsituition jutsu). First, you exploit the weak spot (side stepping quickly and attacking) and use only WEAK attacks (which is swinging the WiiMote rapidly (I only use the WiiMote sorry ><) once you are done the enemy will be in the air, dropping. Quickly use your FireBall Jutsu and watch them burn for a 38hit combo (with full chakra) and the damage just as threatening as a special jutsu. The difference? This is way easier to execute then Sharingan + FULLY CHARGED Chidori (since chidori can be avoided, and since it must be fully charged or near that point, your opponent has time to avoid it.)

I hope this combo helps those people who love Sasuke own more. So far the only people who can avoid this combo is Itachi and Orochimaru as their counters are to go behind. (Shikamaru can avoid it however his counter is slower and if not done beforehand may miss the time and get hit by the full combo anyway)