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.
LeBlanc's ultimate can create fake LeBlancs during her spellcast or, rarely, at a distant position.
The fake LeBlanc created at a distance will always run at the nearest Champion, cast a harmless spell, then immediately disappear.
Attacking LeBlanc first avoids most of her tricks, especially if she's recently used her dash, Distortion.
Stunning or silencing LeBlanc will prevent her from activating the return part of Distortion.
The stat comparisons shown on this page clarify several influential Karthus against LeBlanc counter statistics that may help us interpret the distinctions between the two. As an example, Karthus’s KDA ratio ([kills + assists] / deaths) of NaN is better than LeBlanc’s KDA ratio of NaN, showing that Karthus may be more central to his team's team fighting potential than LeBlanc. This observation is largely a result of the differences in deaths.
Karthus often has a similar longest kill spree as his opponent does. Typically, he takes more damage than LeBlanc. This is usually reflective of differing health capacities, yet it can also imply that the one champion has less agility and thus is not able to escape additional damage when poked or engaged.
Both LoL champions are great. Both champs have their pros and cons. In League's current meta, Karthus usually fairs equally well when playing against LeBlanc, with a 50.6% win rate. Thus, Karthus makes an ok counter to LeBlanc.
While Karthus does have a higher win rate compared to LeBlanc, when facing one another, Karthus also has a lower learning curve that makes him a less time consuming character to learn and master. You should be careful when picking Karthus into LeBlancas his relative depth means you may not be able to reach his full potential without a lot of practice beforehand.
Furthermore, Karthus also has some amount of CC and other utility, a similar amount to LeBlanc. 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 in League of Legends, in Karthus vs LeBlanc matchups, Karthus is the better champ with a similar win rate, less champion complexity, and a similar amount of utility to help out your teammates during team fights.
Karthus is a decent counter to LeBlanc. You will do well by focussing your strategy on increasing your gold and cs and destroying objectives. If you are able to do that, you should be able to stand on your own as Karthus against LeBlanc.
If you would like to learn all of the intricacies of Karthus in order to counter LeBlanc during both the early game and mid / late game phases of League of Legends, you should keep reading to learn a few extra tricks and insights into this matchup. If you listen to the build and suggestions displayed here, you will grow your win rate by a lot and be closer to League of Legends pro players.
Karthus most often gets less CS relative to LeBlanc. Champions who typically don't take much CS usualy don't require much CS to be effective, such as sup champs. These kinds of champions are able to scale properly off of their skills, stats, and first items alone. Yet, champions with large amounts of CS, such as hyper-carries, typically require several high cost items to be effective. In either case, try to surpass the values reported on this page to do well.
The most important items to focus on in your Karthus versus LeBlanc build include Rabadon's Deathcap, Malignance, and Shadowflame. When Karthus used at least these three pieces in his build, he performed significantly better vs. LeBlanc than with most other common item sets. In fact, Karthus boasted an average winrate of 50.6% battling LeBlanc with this counter build.
To have the best probability of crushing LeBlanc as Karthus, you should use the Dark Harvest, Cheap Shot, Eyeball Collection, Ultimate Hunter, Presence of Mind, and Last Stand runes from the Domination and Precision rune sets. Out of all the rune sets players used for Karthus vs LeBlanc fights, this sequence of runes yielded the highest win rate. Notably, these runes averaged a 50.6% win rate overall.
By default, tips, statistics, and builds on how to beat LeBlanc as Karthus are presented for all skill levels, merged. If you want to narrow the statistics and builds to a specific player tier, you may use the selection menu located earlier on the page.