In the championship phreak said that a good karthus will outfarm anybody while not feeding and assisting his team.

orianna does very well in the match up. same with ahri

The problem is that most of his true, hard counters are rarely played in competitive play because they won't scale well into the teamfighting phase. Fizz, for instance, absolutely wrecks Karthus, but nobody ever plays him in tournaments. LeBlanc is the same way.

Burst does a good job. Fizz, Gragas, Xerath...

karthus can safely farm against almost anyone, but that leaves the other mid to roam.

Tf

phreak said it.

Boots.

Eve after level 6 with DFG can blow up karthus in one combo easy. And if he stays at his tower Eve can roam. Eve is solid against Karthus imo.