This build is too risky with the 2 stack items, also why only one score?

Don't like the idea of going hybrid on Kat. And this build seems really risk. One stacking item is risky enough, but Two! Also why would you get SoS? You have no mana. It wouln't help would it?

A few improvements, mainly cause I'm picky xD
Let me also say, that this is by far the best Katarina build I've seen, and I'm doing great with it

1: You level killer instincts to lv 6... might wanna change the lv 16 point.

2: Your items are in the wrong order, you should put Sorc->Mejai->Occult

3: I'm not sure what the reason for this is, but it seems you didn't put a point into Tenacity, what I did was take ur tree and switch the 3 Strength of Spirit into 2 evasion and 1 Tenacity.

You don't need to change all this, as most of it is obvious, but it'd make your build abit easier to figure out. And the Tenacity would make Katarina even less squishy.
Either way, I'm upping this. I've been trying and failing with some other builds, and I'd almost given up on Katarina, but damn, this REALLY works. :D

^I had a similar concept as you did when the patch first came out. Indeed, if you get fed, then this build is unstoppable; however, more often than not, when that starts to happen, the enemy team will target you first.

As Jebus implied, it is very risky to snowball; however, I do agree with you that should you stack, then you should double stack. In the meantime, I will not vote since I haven't tried the build out yet. However, from trying a similar build, when it works, it works marvelously; however, when it fails, it fails miserably. I will have to try it and see.

i stacked Mejai's Soulstealer and Sword of the Occult and in late game my ulti done 300 dmg per dagger this is little bit OP

That was completely my fault - I checked based on a non-updated server and did not notice that her ultimate was buffed. My apologies.

I still stick to my other point that you should never get more than one stacking item.

Awsome build i will try this

http://eu.leagueoflegends.com/news/release-notes-v100107

Katarina

Bouncing Blades
Now scales off of 80% bonus attack damage (instead of 100% of all attack damage)
Base damage increased to 60/95/130/165/200
Now has a 0.35 ability power ratio
Death Lotus
Base damage decreased to 40/50/60 from 50/65/80
Now scales off of both attack damage and ability power rather than one or the other
Now hits the closest 3 targets rather than 3 random targets
Cooldown reduced to 60/55/50 seconds from 60

Wrong. Katarina's ult does not scale with both attack damage and AP. It stacks with EITHER (read the key word there, "EITHER") 55% of her bonus attack damage or 30% of her ability power.

Also, any build where you get more than one stacking item is just unreliable.