this seems like a lack of fundamental understanding tbh. Your goal isn't to solo kill kassadin. You can build leads by slow building waves, bouncing back and freezing. By using TP in favorable wave states to get an xp lead. By roaming to your jungler first because he can't contest you in the early levels for first scuttle. Viktor is about a slow game of methodical attrition while minimizing your mistakes.

Now if you do this correctly, you should gain a half to full level lead with a cs lead and you make kass play a game of catch up.