Against karma, Force a team fight as quickly as you can so Karma isn’t able to poke your team down before you have the chance to engage. Delaying a team fight will allow her to harass your team and make the fight much riskier. 

If Karma uses her empowered Q when trying to poke, you should use the cooldown to start a team fight. When Karma’s Ultimate a is down, she cannot give her team a huge shield d which will make fighting much easier.

Don’t be afraid to invest in an Executioner’s Calling. It will reduce her healing and shielding and it will make winning the team fight a lot easier. Against karma, Delaying a team fight will allow him to harass your team and make the fight much more risky. If Karma uses her self-appointed Q while trying to poke, you should use the cooldown to start a team fight. When Karmas Ultimate is downstairs, she can't give her team a huge shield that will make the fight much easier. Don't be afraid to invest in an execution call. This will reduce her healing and shielding and it will make the victory of the team fight much easier.