Karma is honestly a great champ, you just have to play support, not AP carry. You need to play a champion often more than a few games to be good with them. Karma is a great utility support. THe only problem is she isn't soraka nore Sona. She has a surprisingly high learning curve to play her well.
As for the worst champion I'd have to say Evelyn overall. Her biggest thing was the destealth stun she had. She can still be played well with a TON of ractice, and a lot of luck. But overall she is nothing worth writing home about anymore.
Originally Posted by ExecutionerKen
Karma takes time to learn, and you must have the money to play her (Aka, you can't put her as support)
That will be the only reason why she is underplay, not because she is bad.
She does need that gold, but she is still very useful, easy way to nerf off the gold need is to rune and mastery it in with the GP/5. replace seals and maybe quints for her to generate the gold she needs.