As far as katana's go, besides Raikiri, the best rare one I have found is the Osafune Kanemitsu. Has a higher attack at 263, +14% yokai close combat damage, +19 earth buff and a -17% low attack ki usage. Causes some kind of extra purple damage too
Use the edit function. Don't double post.
The Raikiri is the best weapon in the game but because of scaling you can level yourself up and make some of the loot drop ones stronger just by existing. I don't think the areas in the Alpha are really meant for players over level 30 or so, so you can get some pretty dumb drops for the level of difficulty on subsequent runs.
Just killed that one. Thought it was a player. I found a couple in the first level but they are just names. Something the Something, I forget what they were called but the one I can think of is right at the ambush point with the first miniboss in the first level.
Still failing at killing Nue though... discovered you can keep him in Phase One by not attacking him when his Stamina is depleted.
Nue actually doesn't have a second phase, really. Not in the same way as the first boss. Still attacks in much the same way. Prepare some Water Talismans or just turn on easy mode with the shark Living Weapon and mash normal attack until it dies.
On an unrelated, but cool, note, you can really fuck up an enemy if you stack status effects on them. I stacked fire and lightning on a Stone Sentinel towards the end of the second level and he got a purple aura and got an almost yin yang-like status symbol above his life bar. I think it only happens when you put more than one effect on an enemy. Going to experiment with this later.