Katarina - The Sinister Blade is at the moment a really strong champion, this champion is perfect in teamfights since her Ultimate is AoE and does TONS of damage. Katarina fits perfectly with Amumu, their Ultimates is the perfect combination. Amumu does his Bandage Toss and than Ultimates the whole enemy team. When the enemys are stunned, Katarina jumps in and kills all of them by using Q -> E -> W -> R, this combination will be a Penta machine!
If you max your W it´s improtant to build "Bilgewater Cutlass" Before "Hextech Revolver" because it scales more with Attack Damage.

Keep in mind to poke alot during the laning phase, for example: you´re against Annie. Use your Q -> E -> W, and run away, when you´re sure you can kill the enemy you just simple chase whilst spamming your W since it has a really low cd.

Let your team dive in first, than you use Q -> E -> W -> R for maximum damage. This is the time when you decide if you wanna buy Zhonya´s Hourglass pretty early or as your last item. The enemy will probably try to kill you when you´re using your Ultimate, so it will be usefull to have a defensive item.

Since Katarina doesn´t use mana, you can spam your Abilities on creeps, Q -> E -> W.

Thanks for checking out this guide, hope you like it!

Youtube: Youtube.com/Trekojz
TwitchTV: twitch.tv/Trekojz