Vayne kinda does everything Kai'sa does but better
The only exception might be Kai'sa's ability to get into the backline, but Vayne is all around better. Kai'sa is only on par with other adc's lategame and even then she's just average. Im not saying Kai'sa is terrible and needs huge buffs; Kai'sa is just mediocre. I kinda feels like playing Ezreal or Mf support when playing Kai'sa. She doesn't really feel like the main damage dealer.