a proper way to fix kassadin for good.
give him a skin in the next pbe cycle and some balance changes to settle him down for good. the balance changes shouldn't be much just his base stats/base damage buffs. (tbh his q's damage should stay the same since you can spam it but it's shield may need some buffs because it's pretty small) his E on the other hand needs a buff that is small to make it balanced and not broken base damage increased to 200-240 depends on how it works out and make it use able when it reaches 3 stacks but with a lower damage ofc. his ultimate doesn't deal any damage so adding 2 ap Ratios to it might help but as i said it needs to be tested and adjusted properly . which means you can't simply say he will get still be weak/become op or broken since it's not tested.