Timing Janna's ultimate can push enemies away from a wounded ally or even separate enemies.
Eye of the Storm can be used on allied turrets.
Quickly firing a Howling Gale without the charge up can be used to heavily disable the other team.
Karthus can cast spells for a short duration after he is killed. Move away from his corpse to be safe.
Make sure you always have enough health to survive Requiem, even if you have to go back to the base more frequently to heal.
The stats shown here show several influential Janna versus Karthus matchup stats that may help us figure out the distinctions between this pair of champs. Janna’s KDA ratio ([kills + assists] / deaths) of NaN is better than Karthus’s ratio of NaN, demonstrating that Janna may be more central to her team's team fighting effectiveness than Karthus. This observation is in large part caused by the differences in assists.
Janna often has a significantly smaller longest kill spree than her foe does. On average, she receives less damage than Karthus. This often reflects different amounts of tankyness; however, it can also show that the champ with more health has less agility and thus is not able to escape further harm when engaged or poked.
Both League champions are great champions. Both have their pros and cons. In the game's current meta, Janna usually wins when taking on Karthus, with a 57.8% win rate. Therefore, Janna makes a fantastic counter for Karthus.
While Janna does have a much higher winrate than Karthus, when on opposite teams, Janna also has a greater learning curve that makes her a more difficult character to develop with. You should be be fine when picking Janna into Karthusas her relative depth means you may not be able to reach her full potential without a lot of practice beforehand.
Furthermore, Janna has a lot of CC and other utility, a similar amount to Karthus. This makes her just as valuable during teamfights, especially when facing champions with a ton of burst damage.
While there is not one best champion for every situation in League of Legends, in Janna vs Karthus matchups, Janna is the better champion with a noticably higher win rate, similar champion depth, and a similar amount of utility to help out your allies during teamfights.
Janna is a great counter to Karthus. Focus your actions on keeping up your gold and cs and taking out objectives. If you do that, you should do very well as Janna against Karthus.
To truly master Janna in order to counter Karthus during both the lane and mid / late game phases of League of Legends, you should continue reading to learn a few extra tricks and insights into this matchup. If you listen to the build and suggestions shown above, you should increase your win rate by a lot and be closer to League of Legends pro players.
Janna usually accumulates a lot less CS relative to Karthus. Champs who on average don't acquire many minion kills typically don't have to have much CS to be valuable teammates, such as support champions. These kinds of champions are able to scale well off of their abilities and first items alone. Yet, champs with a lot of CS, such as hyper-carries, often need a lot of items to be effective. In either situation, try to do better than the values shown here to do well.
The best items to have in your Janna versus Karthus build consist of Redemption, Ardent Censer, and Moonstone Renewer. When Janna incorporated at least these three items in her build, she did much better vs. Karthus than with most other commonly used item sets. In fact, Janna had an average winrate of 57.8% when playing against Karthus with this build.
To have the best chance of defeating Karthus as Janna, you should use the Glacial Augment, Magical Footwear, Biscuit Delivery, Cosmic Insight, Font of Life, and Revitalize runes from the Inspiration and Resolve rune sets. Out of all the rune combinations players used for Janna vs Karthus counters, this blending of runes yielded the greatest win rate. Moreover, these runes averaged a 57.8% winrate overall.
If you want to get Janna vs Karthus tips and counter builds for a a distinct rank, feel free to select one from the selection menu displayed above. If viewing for the first time, the statistics and build suggestions given are calculated using all games finished with both champions.