I-Ninja

Battle Arena:
To unlock the Battle Arena, get all the grades. You should then get the Master grade. The Battle Arena will now be open in Robot Beach.
Burningundam3241.

Hint: Defeating Malakai:
In the first part (where there is lava for a field), keep a steady pace while jumping around on the stones. Hold [Forward] and the direction that you want to jump and collect the shuriken. Throw it at him without locking on. After throwing the full amount of eight shuriken three or four times, he will fall down into the lava. Then, he will jump up and absorb the lava. You will now have to sword fight him. The Soul Sword and Revive Rage are recommended for this. If you run at him and slash repeatedly, you are going to get hammered. The best times to attack him are when he just finishes a quick slash and when he is just about to do the non-shock wave ground pound. Hit him at those times and use Berserks and Insane Rages every time you do not need to revive.
SCARREDBARDOCK.

Hint: Defeating O-Dor:
Attack his belt. After you attack it twice, he will slam his fist. You can now attack it two more times before he slams you away.
Djgamemaster2008.

Hint: Defeating Psyamon:
To damage Psyamon, you will have to use your Power Bolt attack. Just shooting him with your miniguns will not effect him. Psyamon will shoot a red ball of energy at you. If it hits you, it will do a significant amount of damage. To avoid it, shoot at it with your miniguns to blow it up. He will then open his mouth and release Wraith Ranx (ghost-type Ranxs) at you. Shoot at them as fast as you can, as he will release a lot of them. When you kill one of them, your Power Bolt gauge (the gauge at the bottom right corner of the screen) will rise. When the gauge is full, you will be able to shoot your Power Bolts at Psyamon. As the battle continues, Psyamon will get much tougher. For example, after you damage him once, he will also shoot a blue ball of energy at you. If it hits you, your robot suit will malfunction, causing your movement to fail. To avoid it, shoot at it. He will also release more Wraith Ranx at you. Repeat the process five times to kill Psyamon.
Rapforeva65.

Hint: Get stronger swords:
To get stronger swords, you have to kill enemies. Notice that when you complete a mission (at the blue screen with Ninja floating), there is a sword at the bottom of the screen called "Ranx Bank". The sword has numbers that increase with the more "Ranx" that you kill. Also, the more "Ranx" you kill, the sword gets covered in Ranx blood. When the sword is full of Ranx blood, at the "Mission Complete" screen, Ninja will be holding his old sword. He will drop the old sword and a new one will fall into his hands.
SCARREDBARDOCK.

Hint: Sword list:
Notice that the sword color changes in the your belt changes.
Rolliecat78.

1. Ninja's Sword
2. Golden Sword
3. Jade Sword
4. Sapphire Sword
5. Fire Sword
6. Soul Sword

Hint: Rage skills:
Redeyezbdrag0n.

First skill: Ninja Berserk
Second skill: Ninja Revive
Third skill: Ninja Shuriken
Fourth skill: Lightning Rage

Hint: Mow grass:
Where there are grass, flowers, mushrooms, other foliage, objects other than crates and barrels, and certain decorative objects, you can cut them down to earn a few extra points towards your main score. This is useful in the certain levels that require a high score to earn the grade.
ateortbhbuKristofer Doege.

Hint: xPower-Ups:
Whenever you kill an enemy in a rapid succession, the number to the right of the health bar increases by one up to 10. This represents what points you receive for killing an enemy, multiplied by the number displayed. This is useful in certain missions where a high score is required to earn the grade.
Kristofer Doege.

For an easy X2 Point boost, When you are grinding on a rail jump off, but land on the rail again. "X2" should appear by your level points.
Redeyezbdrag0n.

Hint: Healing:
If you are low on health, try to find some weeds and chop them down. Notice that your Rage Ability switch will gradually increase. Keep chopping down weeds and you will soon be able to use your "Ninja Revive" to heal yourself.
Rob Webster.

If you are low on health, use the Ninja Fury. You will recover some health.
julian mata.

You do not necessarily need a Healing rage to get healed. Just use any rage to get healed slightly, although Revive gives you more health.
Redeyezbdrag0n.