The Voidreaver - Kha'Zix is one of a couple of Champions coming from the enigmatic region of The Void. He boasts high damage at all stages of the game and a very adaptable playstyle depending on how the game is turning out thanks to his evolve mechanic. Kha'Zix is an attack damage assassin, he'll look to snowball ahead in the early game by picking people off, and will likely transition to the mid game to a more splitpush role if he did manage to get ahead, thus applying pressure in the side lanes, giving his team more gold, and eventually forcing one or more people to come deal with him or else risk losing too many objective to recover from.
Passive – Travelers Call
Kha'Zix gains Unseen Threat when the enemy team loses Sight icon sight of him, causing his next basic attack against an enemy champion to deal bonus magic damage and slow them by 25% for 2 seconds.
Q – Cosmic Binding
PASSIVE: Kha'Zix marks all visible enemies who aren't accompanied by any of their allies nearby as Isolated.
ACTIVE: Kha'Zix slashes the target enemy, dealing physical damage, increased by 30% against isolated targets.
EVOLVED ENLARGED CLAWS: Kha'Zix gains 50 bonus range on his basic attacks and Taste Their Fear, which also deals bonus physical damage to Isolated targets.
W – Caretakers Shrine
Kha'Zix fires a cluster of spikes in a line that detonates upon hitting an enemy, Slow icon slowing all enemies in a small area by 20% for 2 seconds and dealing them physical damage, increased by 20% against monsters.
Kha'Zix heals himself if he is within detonation radius.
EVOLVED SPIKE RACKS: Void Spike fires three clusters in a cone, Slow icon slows by 50% and grants Sight icon sight of enemy champions hit for 2 seconds. Multiple explosions do not deal extra damage to the same target or provide Kha'Zix with additional healing
E – Magical Journey
ACTIVE: Kha'Zix leaps to the target location, dealing physical damage to nearby enemies upon landing.
EVOLVED WINGS: Leap gains range and its cooldown is reset on enemy champion takedowns.
R – Tempered Fate
PASSIVE: Each rank in Void Assault allows Kha'Zix to evolve one of his abilities, granting it additional effects.
ACTIVE: Kha'Zix enters Void Assault 2 stealth for 1 second, acquiring Unseen Threat, gaining 40% bonus movement speed, and Ghost ghosting while Void Assault 2 stealthed. - After 2 seconds of leaving Void Assault 2 stealth, and for the next 15 seconds, Void Assault can be cast a second time at no additional cost.
EVOLVED ACTIVE CAMOUFLAGE: Void Assault can be cast a total of 3 times and each instance grants 2 seconds of Void Assault 2 stealth
Kha'Zix is the definition of a "1v1 Me" champion. He gains damage from fighting you if you're alone, unfortunately for him, there are towers, minions and four other champions that don't want to see you die. Keep an easy escape to any of these things, and Kha'Zix becomes a great deal weaker in any of fight.
Kha'Zix isn't tanky early, that means in the early game, he has one of two options. Take his own buffs and do a standard clear, or take one buff, and come try and fight you at yours. He probably won't do the second one, just because of how much damage he takes, and how much time he can waste, however, if you're a strong counterjungler, you can find and kill him. Any tank or high damage-early pressure jungler will give Kha'Zix a hard time and force him to run in early engagements.
Kha'Zix is an AD Caster, that means he's reliant on having abilities up. Some of these abilities have extremely long cooldowns, such as Leap and Void Assault. For every ability down, Kha'Zix becomes weaker. The only cooldown he has that's up more than two times in a one on one fight early is Taste Their Fear, and that doesn't do enough damage alone to kill most standard junglers.
Elise just doesn't ever have to be isolated. The moment she becomes a spider, she has spiderlings that prevent isolation, and also beat on Kha'Zix in any early one on one. She sustains through the jungle better than he could ever hope to and has high base damages besides. She's an early pressure jungler so she also has the option of playing standard and simply making a larger impact than him, snowballing her lanes and winning the game for her team while he struggles to become as relevant.
If you've ever watched this matchup you now how sad it can be. Volibear has a lot of health to begin with, and with the health scaling damage on his W, he just doesn't care about fighting Kha'Zix. He's also another one of those champions with pretty decent ganks at levels 3+ and can pressure out summoner spells for his team, certainly outpressuring a level 3 Kha'Zix. Volibear sustains well in the jungle, and with his passive, has the option of just looking for Kha'Zix and beating him senseless in his own jungle, since Kha willnever win an early one on one against the bear.
Even with the nerfs, Gragas still comes in with CC, damage reduction, superior sustain and a lot of early damage on both W and Q. Not only does this allow him to take On Kha'Zix in early one on ones but at level six and above, he can even peel Kha'Zix off of his teammates using his explosive cask, causing the bug to lose one of his biggest strengths: The freedom to choose all of his fights.
This guy is basically the answer to all of your problems against Kha'Zix. All Lee Sin wants to do is punish this guy for being so low in the jungle. If Lee Sin catches him low, and he will, given all his mobility, he lands a Q and destroys him with the execute damage. If Kha'Zix tries to stealth away, Lee Sin lands a Q and makes him visible, follows it up, and hits E as Kha'Zix re-stealths, keeping him visible. If Kha'Zix tries to jump on one of Lee's teammates, Lee kicks him away. Not only that, but Lee Sin massively outperforms Kha'Zix in the art of the low level gank. It's a bad time for the bug.
Being against an AD Assassin, it's best to itemize armor. Randuins Omen has a lot of value in any matchup against Kha'Zix, it can hinder his chase potential if his jump is down. Cinderhulk is obviously worth building on any tank, and the multiplicative health passive makes it even better against Kha'Zix, along with the Bami's Cinder passive giving extra damage against him for being too close. Skirmishers is a good item to build in solo que, or if you intend to get a sightstone in organized play, as the Challenging Smite reveals Kha'Zix for four seconds and increases your damage against him.