Katarina is the AP-carry in your game, she is fast in her combo's, take's out enemies with ease. She is what you need to win a game if needed. She can be 1 of your easiest champions or your hardest I takes practice to get the strikes and blows efficiently.

Pros:
+okay early game
+strong Middle game
+ incredible Late Game
+fun
+doesn't use mana so you can just skill spam
Con's:
-worst enemy is CC