Lay Waste is very strong at farming minions and harassing enemy champions.
Ask your allies to help point out when you should use Requiem to get kills in different lanes.
Save an interrupt ability for when Janna uses her ultimate.
Listen for the charge up sound on Howling Gale in case Janna is trying to hit you with it from off screen or from brush.
Janna's at her strongest when buffing another ally. If you can harass her ally, it will weaken her ability to fight you.
The stat comparisons shown here underscore several influential Karthus vs. Janna counter statistics that can help us explain the differences and similarities between the pair. As an example, Karthus’s KDA ratio ([kills + assists] / deaths) of NaN is better than Janna’s KDA ratio of NaN, indicating that Karthus may be more central to his team's team fighting effectiveness than Janna. This observation is in large part caused by the differences in killsdeaths.
Karthus typically has a much larger longest killing spree than his enemy does. Typically, he takes more damage than Janna. This typically indicates differing health capacities, yet it can also hint that the champion with increased HP has less mobility and thus is not able to kite away from further damage when engaged or poked.
Both League of Legends champs are great champions. Both champs have their strengths, weaknesses, and counters. In League's current meta, Karthus usually loses when playing against Janna, with a 45.4% win rate. Thus, Karthus makes a bad counter to Janna.
While Karthus does have a much lower win rate compared to Janna, when on opposite teams, Karthus also has a greater difficulty level that makes him a more difficult character to pick up and master. You may get destroyed when picking Karthus into Jannaas his relative depth means that you may not be able to reach his full potential without a significant amount of practice beforehand.
Furthermore, Karthus also has some amount of utility and CC, a similar amount to Janna. This makes her just as valuable during teamfights, especially when facing champions with a ton of burst damage.
While there is not a single best champion in League of Legends, in Karthus vs Janna matchups, Janna is the better champion with a much lower win rate, similar champion depth, and a similar amount of utility to help out your allies during late stage team fights.
Karthus is a terribly counter for Janna. You will do well by focussing your tactics on keeping up your gold income and clearing objectives. If you can do that, you should be able to stand on your own as Karthus against Janna.
To learn all of the intricacies of Karthus in order to counter Janna during both the lane and mid / late game phases of League of Legends, you should keep reading to gather a few extra lessons on this matchup. If you listen to the build and stats presented here, you will grow your win rate significantly and be that much closer to League of Legends pro players.
Karthus on average accumulates much more CS as Janna. Champs who typically don't acquire much CS often don't have to have much CS to be effective, such as supports. They are capable of scaling properly off of their abilities and first items alone. Yet, champs with a lot of CS, such as hyper-carries, often have to have a lot of items to be effective. In either case, try to do better than the values displayed here to do well.
The most crucial items to focus on in your Karthus versus Janna build consist of Liandry's Anguish, Void Staff, and Shadowflame. When Karthus used at least these three items in his build, he performed significantly better when fighting Janna than with many other common counter builds. In fact, Karthus had an average win rate of 45.4% when countering Janna with these items in his kit.
To have the greatest chance of beating Janna as Karthus, Karthus players should use the Dark Harvest, Cheap Shot, Eyeball Collection, Treasure Hunter, Presence of Mind, and Last Stand runes from the Domination and Precision rune sets. Of all the rune builds players picked for Karthus vs Janna matchups, this sequence of runes resulted in the best win rate. Moreover, these runes provided a 45.4% win rate overall.
If you need to get Karthus x Janna tips and counter builds for a an individual skill level, please choose one from the selection menu displayed above. If viewing for the first time, the stats and guides displayed are calculated using all rounds played with these champs.