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.
Body Slam is on a very low cooldown, making it difficult to pursue Gragas. Don't overextend yourself chasing him.
Gragas can knock everybody away with his ultimate. Be careful that you don't get knocked into him or, worse, an enemy tower.
The stats shown on this page show several strategic Karthus vs. Gragas counter statistics that can help us appreciate the differences between this pair of champions. For instance, Karthus’s KDA ratio ([kills + assists] / deaths) of NaN is more than Gragas’s KDA ratio of NaN, indicating that Karthus may be more central to his team's team fighting capability than Gragas..
Karthus usually has a similar longest killing spree as his opponent does. On average, he takes a similar amount of damage to Gragas. This is usually reflective of different amounts of tankyness, but it can also hint that the one champ has less agility and thus is unable to escape additional damage when poked or engaged.
Both League champs are great. Both have their pros and cons. In League's current meta, Karthus usually loses when trying to fight Gragas, with a 47.5% win rate. As a result, Karthus makes a bad counter for Gragas.
While Karthus does have a lower win rate than Gragas, when facing one another, Karthus also has a greater level of difficulty that makes him a more time consuming champion to pick up and master. You should be very concerned when picking Karthus into Gragasas his relative depth means that you may not be able to unleash his full potential without a lot of practice beforehand.
Additionally, Karthus has some amount of utility and CC, a similar amount to Gragas. This often makes her just as valuable during team fights, especially when fighting champions with a lot of burst damage.
While there isn't a single best champion overall in League of Legends, in Karthus vs Gragas matchups, Gragas is the better champ with a lower win rate, more champion depth, and a similar amount of utility to help out your teammates during team fights.
Karthus is a garbage counter for Gragas. You will do well by focussing your tactics on increasing your gold income and taking out objectives. If you are able to do that, you should be able to stand on your own as Karthus against Gragas.
If you would like to truly master Karthus in order to counter Gragas during both the laning and mid / late game phases of League of Legends, you should keep reading to gather a few extra tricks and insights into this matchup. If you mind the build and suggestions shown here, you should increase your win rate significantly and be that much closer to League of Legends pro players.
Karthus often accumulates a similar amount of CS relative to Gragas. Champs who typically don't get many minion kills often don't need much CS to be valuable teammates, such as supports. They are capable of scaling well off of their abilities and first items alone. Yet, champions with large amounts of CS, such as hyper-carries, typically have to have a lot of items to be effective. In either case, try to do better than the values shown here to do well.
The most crucial items to focus on in your Karthus versus Gragas build include Rabadon's Deathcap, Shadowflame, and Liandry's Torment. When Karthus used at least these three items in his build, he performed much better vs. Gragas than with most other common counter builds. In fact, Karthus boasted an average win rate of 47.5% when countering Gragas with this counter build.
To have the highest chance of beating Gragas as Karthus, you should equip the Dark Harvest, Cheap Shot, Eyeball Collection, Ultimate Hunter, Gathering Storm, and Transcendence runes from the Domination and Sorcery rune sets. Out of all the rune sets players used for Karthus vs Gragas counters, this mixture of runes resulted in the best win rate. In fact, these runes averaged a 47.5% winrate overall.
By default, tips, statistics, and builds on how to beat Gragas as Karthus are displayed for all skill levels combined. To scope the statistics and builds to a specific skill level, you can use the selection menu located above.