Make sure you reposition and move away from Katarina’s Blade drops. This will reduce her ability to trade and kill you with her E.
Don’t blindly follow Katarina’s roams or you might get ambushed Punish her by pushing the wave into her turret whenever she leaves the lane.
One of Katarina’s weaknesses is her lack of range. When playing as a ranged champion, whenever she moves forward to last hit, try to harass her with abilities and auto-attacks. Make sure you watch your positioning though so she doesn’t try to all-in you in return.
Hold on to your CC abilities until Katarina has engaged. If you can interrupt her as soon as she channels her Ultimate R, her damage output will be low and you’ll have a higher chance of winning the team fight.
Avoid fighting in areas that are tight and enclosed. Katarina has insane AOE damage and if your team is grouped closely together, she will be able to melt you down. Try and fight in areas that leave your team split slightly apart.
Forcing a team fight when Katarina’s Zhonyas is down is a good way of taking her out of the team fight quickly. This will reduce her ability to take over the team fight with her resets.
Katarina’s major power spike comes with finishing Hextech Gunblade- giving her more sustain and more burst damage. Upon finishing Hextech Gunblade, Katarina will force more skirmishes and trades.
Once Katarina hits level 6, her kill pressure will intensify as her Ultimate R is a great tool and deals tons of damage. Respect her all-in once she hits level 6.
Katarina is really good in team fights. Make sure you lock her down with CC as soon as she engages so she cannot get a good Ultimate R off.