With this guide i wanna show you how insanely katarina can be (even more).

The masteries are variable, but you should take the 21 points in 'Offense' just like me. The rest is up to yours ;)

Mostly you should do it like me, because you have to remember one thing: 'Sinister Steel' has a low cooldown, so with this item build, it has even less cooldown and deals LOTS of dmg. So i would advise maxing it before 'Bouncing Blades'.

Your items are the most important part to let this guide work..
So you need to buy 'Ionian Boots' and 'Morello's'. The good thing is: 'Morello's' will give you some nice ability power too, so we wont lose the dmg. 'Rabbadon's' is a must have to deal dmg, so i dont have to explain it.. After buying these items I would advise you to fast buy 'Guardian' because the more dmg you deal the more you will get focused and you dont need much time to deal dmg, so your restored 750 hp from guardian will be enough to do a massacre ;D
Now you can store your life up for even less dying ('Rylai's') and get more dmg ('Void Staff')..

Tip:
You need to find out, what is the best order for you respective 'Ionian Boots' and 'Morello's'... It can be different every time, just depending on your opponent. Mostly buy 'Morello's' for early dmg and 'Ionian Boots' for even earlier spam.

I dont have to tell you, how insanly you will get farm xD 'Sinister Steel' + 'Bouncing Blades' and low cooldown = free farm.. You mostly will have the biggest farm ;) with distance to others :X

With that guide, you are able to help your team much more by spamming the hell out of your opponents - espacially in team fights additional with your passive (ulti-ulti-ulti) ;D

Pros:
-insane dmg output with spam ability (espacially with 'Sinister Steel')
-being able to use your ulti even more often in team fights
-(mostly) biggest farm
-escaping/ hunting great with low cooldown 'Shunpo'

Cons:
-little less ability power than you could have (that doesnt matter because of your cooldown reduction)
-you probably will get focused even more, but they will notice its dangerous/ useless ;)