How to beat the kat?
I've noticed way too many of my games just come down to whoever has a kat wins. And no, it's not that my team fails to stop her ult. In fact, I often use Janna and just press r right when she ults and stop her ult almost completely. And yet, she still just carries their team and can just win 1v5 without even needing her ult. It seems that just pressing eqw does too much damage. Is there any good counter play for this? It's so hard when she chooses when she does it and it's so hard to do anything to her when she doesn't go in.
? XD Also i just ban her (katarina) any chance i get lol.

help your team, and
helps you. Since Kat is technically an apc, she is a priority for cc, so save your cc specifically for her. Not just cc her, save your cc specifically for her. A good Kat waits until all the cc is used on the tank, then hops in for a pentakill.
I believe has a kit that essentially counters her (true damage melee ult when she ults, more sustain, better cc, can silence to prevent low health escapes).
will make her life hell in teamfights.