Originally Posted by Borigrad
Very few champs can stop a competent Kassadin from CSing.
It's really not even difficult pre-6.
You run up and auto attack him and he's like, "Oh yeah, well here's a Null Sphere, jerk!"
Then you just tell him, "Yeah yeah, here's *insert your champion's harass spell here* and another two auto attacks for every CS you got."
Sure you'll take damage, but he'll take a lot more and because he's melee he can't CS while low, you can as a ranged champion. He also can't CS well using Null Sphere since its mana cost isn't too friendly and its cooldown isn't the best.
Beating Kassadin pre-6 is literally as simple as just auto attacking him all the time, after 6 is where things get difficult, since he gets free harass and around rank 3 is where Null Sphere harass starts hurting a lot.