Rengar vs Karthus Counter Pick

Karthus opens with 21 base armor and 46 base attack damage, and Rengar’s 54.9% across 299 logged games from patch 16.13.1 follows from those two numbers. Unseen Predator turns any attack launched from brush into a leap, and Savagery at full Ferocity removes most of a 620-health body before a mage with 450 attack range gets to use it.

Death Defied is the complication. Karthus keeps casting in spirit form after dying, so a successful kill does not end his contribution: Defile continues draining nearby enemies and Requiem can still be channeled for three seconds afterwards. Rengar’s own exit matters accordingly—Thrill of the Hunt camouflages him while revealing the nearest enemy champion, and Battle Roar heals from damage recently taken, which covers the spirit-form window.

Wall of Pain is the counterplay worth respecting. Anything passing through it loses movement speed and magic resist, and Rengar’s 345 base movement speed against 335 is his main asset in a chase. Approaching from an angle the wall does not cover, or waiting until it has been spent, decides whether the burst connects at all. Difficulty ratings of 7 and 8 mean neither pilot has it easy, but the pressure sits with the mage: 2,490 health at level 18 arrives with only 100.9 armor, and 46 base attack damage offers nothing in a direct fight.