Fizz's spells scale off Ability Power - consider getting items like Zhonya's Hourglass or Banshee's Veil against teams that have high burst threat - and items like Lich Bane or Rabadon's Deathcap if you think you can survive without the Health.
Since Fizz can move through units, find opportunities in lane to walk through minions and apply Seastone Trident's passive - following it up with the ability's active attack after a few seconds.
Fizz's ultimate ability, Chum the Waters, can be aimed at an enemy or towards the area where you think they'll be going.
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 stat comparisons shown on this page underscore some valuable Fizz vs. Karthus matchup stats that may help us figure out the differences between this pair of champs. As an example, Fizz’s KDA ratio ([kills + assists] / deaths) of NaN is more than Karthus’s ratio of NaN, demonstrating that Fizz may be more central to his team's team fighting potential than Karthus. This observation is largely a result of the difference in kills.
Fizz often has a much larger longest kill spree than his matchup does. On average, he receives less damage than Karthus. This is usually reflective of differing health capacities, yet it can also show that the champ with higher HP has less mobility and thus is unable to flee from further harm when engaged or poked.
Both League champions are great champions. Both have their strengths, weaknesses, and counters. In the game's current meta, Fizz usually wins when playing against Karthus, with a 54.4% win rate. As a result, Fizz makes a great counter for Karthus.
While Fizz does have a much higher win rate than Karthus, when they face off with one another, Fizz also has a lower level of difficulty that makes him a less challenging champion to pick up and master. You should be be fine when picking Fizz into Karthus.
Additionally, Fizz also has almost no amount of utility and CC, a similar amount to Karthus. This often makes her just as valuable during team fights, especially when facing champions with a lot of burst damage.
While there isn't a single best champion for every situation in League of Legends, in Fizz vs Karthus matchups, Fizz is the better champ with a noticably higher win rate, less champion complexity, and a similar amount of utility to help out your allies during teamfights.
Fizz is a great counter to Karthus. Focus your actions on increasing your gold income and clearing objectives. If you are able to do that, you should do very well as Fizz against Karthus.
To learn all of the intricacies of Fizz in order to counter Karthus during both the lane and mid / late game phases of League of Legends, you should keep reading to pick up a few extra tips and tricks for this matchup. If you pay attention to the build and stats presented here, you will grow your win rate by a lot and be closer to League of Legends pro players.
Fizz typically gets more CS as Karthus. Champions who typically don't take many minion kills often don't have to have much CS to be valuable teammates, such as supports. These kinds of champions are capable of scaling properly off of their skills, stats, and first items alone. Yet, champs with a lot of CS, such as hyper-carries, typically have to have several high cost items to be effective. In either case, try to do better than the numbers shown on this page to do well.
The ideal items to prioritize in your Fizz versus Karthus build include Rabadon's Deathcap, Lich Bane, and Shadowflame. When Fizz incorporated at least these three pieces in his build, he performed significantly better when fighting Karthus than with most other common builds. In fact, Fizz boasted an average win rate of 54.4% battling Karthus with this build.
To have the greatest chance of annihilating Karthus as Fizz, you should use the Electrocute, Sudden Impact, Eyeball Collection, Treasure Hunter, Triumph, and Coup de Grace runes from the Domination and Precision rune sets. Of all the rune builds we have analyed for Fizz vs Karthus counters, this sequence of runes resulted in the best win rate. Moreover, these runes gave a 54.4% win rate overall.
If you would like to see Fizz versus Karthus tips and counter builds for a a specific division, feel free to select one from the selection menu shown above. At first, the stats and strategies given are calculated using all games completed with both champs.