Level and lives select options:
Go to the main menu and hold down X + O on controller 2 while having Options selected to choose the following: how many lives you start with (up to 9), your starting stage, and play at the Very Easy and Mania difficulty levels.
No damage from throws:
To avoid damage when being thrown by an enemy, press and hold UP+JUMP from the moment you are thrown until you hit the ground. Your character will land on their feet and sustain no damage.
Pipe Wielder - Wield the pipe in single-player or co-op mode.
Knife Wielder - Wield the knife in single player or co-op mode.
Psycho - Kill 10 enemies without losing your weapon.
Perfect Boss - Complete the first boss without dying.
First Versus - Complete another player in an online versus match.
Online Co-op - Complete an online co-op mode.
Kill Jet - Defeat Boss 'Jet' at the end of Stage 2 -- with Game Settings set to Hardcore.
Online Warrior - Complete 10 opponents in online versus match.
Fourth Boss - Complete the fourth boss.
High Score - Score 800,000 points in one game -- with Game Settings set to Hardcore.
Hard Win - Complete the game without using a special attack.
Perfect Win - Complete the game without continuing.