I'm going to shed some light on Kalista for you noobs.
She's an ADC that counters melee. In an extremely annoying and badly designed way, but it's what she does and the counterplay IS there.
Reduce her attack speed.
Malphite
Randuin's
Frozen Heart
She's CertainlyT's only toxic champion. He hasn't failed outright with her (and he honestly never has) but this is his only big mistake. As my favorite designer he has let me down. But make no mistake that just because Kalista is badly designed doesn't mean she's overpowered. She's just...DUMB. The counterplay is there. Stop picking melee champions against her. If some idiot that goes on the forums and sees the complaints first picks Kalista in ranked thinking she's freelo, pick Malphite or rush Frozen Heart/Randuin's. Do something. Don't just sit there and cry and beg for nerfs. She's supposed to counterpick melee bruisers and assassins, not be a first pick.
So as annoying and stupid as she is, CertainlyT wasn't entirely blind in her ideation (he never has been.) He knew attack speed reduction would be a counter for her. But he didn't realize how toxic she is when she works.
Disclaimer: I do not own her or play her and find her extremely fucking annoying as an Assassin main. But I'm also knowledgeable about the game; something many people here lack in vast amounts.