To use a character's special attack, press the X button when your character's chakra is full. These attacks are powerful, and if used at the right time, can defeat your opponent. To name a few, there is Kakashi's Chidori (Lightning Blade), Naruto's Clone Barrage, Zabuza's Silent Killing Technique, and Lee's Forward Lotus. Or if you're in a tight situation, you can just press the L or R button to use the Replacement Jutsu.