The dragon sword at level 3 is all you will need.
While the above is technically "true" - not only can the same be said for (almost?) every weapon in the game... it's not what was asked. (I believe there may be an achievement for completing the game using only one of the weapons - one for each weapon, so you only "need" one weapon - any one should do, though of course some are better than others) ;
The most obvious better weapon is The True Dragon Sword - The Dragon Sword at level 4. However, the question (and answer) is more complicated than that. The two main things that complicate the issue are your playing style and the particular enemy you're fighting. Some weapons are better at killing certain enemies than other weapons.
But if you level the playing field, and consider "the best weapon" to play through the entire game - for most players... you could easily pick The Dragon Sword at level 4. However, other possible weapons could also easily be the Eclipse Scythe, the Lunar Staff, and the Dragon Claw & Tiger Fang at level 4. Personally, for example, I'd say the Scythe is probably top, then the Lunar, True Dragon Sword, and Dragon Claw/Tiger Fang. (But I'm not a great player, so hard to say if that's a prime example)
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The third projectile weapon is an empty slot, it was removed from the game. It was the spear gun from Ninja Gaiden Black and Ninja Gaiden Sigma 1.
no... in ninja gaiden 2 you cant play with another character.. only in the sigma seriesou can play with someone else!
maybe try if you the cheat
There are around 20 levels in Ninja Gaiden 2, each level increasing in difficulty. Also here are some secrets too defeating the 3 greater feinds With Alexi, your best bet is the Dragon sword because it is more agile and you can use the Reverse Wind Technique. Volf is really easy to beat. He just charges at you. Zendonious takes awhile. Your best bet is the Eclipse Scythe. Use the dash and Y to hit him. Also attack him when he raises fire from the ground.
yes you can. up on d-pad and switch over to anther weapons and press a+b