Why does Kai'sa feel overbearing even if her winrate isn't that high?
TL;DR: Kai'sa's issue is not entirely her damage, but rather her massive Range and potential that scares enemies.
Introduction:
Vayne and Kai'sa are two hypercarries that have nearly unrivaled late games with near full builds/full builds. Why are they so universally powerful then? What is it in their kit that allows them to function so efficiently?
Let's explore what they typically do to preface this post.
Vayne:
Vayne is a lockdown champ/rapid fighter, and also typically a very safe ADC in teamfights.
Do NOT argue with me on this. Repositioning on a 1.8 second cooldown with self peel and invisibility for 1 second each time you reposition is very easy to take advantage of. She excels in smoking down 1 target after another while the rest of her team does their best to stall out the teamfight/buff the Vayne, especially with her ult gaining extra duration with each champion death.
"BuT MUH VaAYHNE FLASHY plAYS"
Vayne can make flashy plays, just like most of the champions in the game. That doesn't mean that that's all she does. When played right, Vayne usually doesn't die. Ever. Even then, she'll usually 1v1 each champion as fast as she can before moving on to the next.
Here's an explanation of Vayne's 1v1 potential assuming she gets caught out of position with no team support in sight, assuming the Vayne knows what Zed is capable of, and respects the auto-attack distance:
Vayne: Auto attacks Zed
Zed: R. If Zed has to use W to engage, it's a free win for Vayne.
Vayne: Ult + Dash once the mark hits.
Zed: Throw shurikens. It's impossible to land a second shuriken if Vayne uses her Q alone, and Zed ulted at max range.
Zed's max R range: 625 units. Vayne's Tumble range: 300 units. That's 925 units already, and include Vayne's movement speed of 330 + boots and before Zed's R animation is over she can get her hitbox out of any potential second Q range.
Vayne: Repeatedly attacks Zed, slowing him witn BoTRK, and Q-ing and E-ing him if he uses W to get close.
Vayne: Also repeatedly dashes in and out of invisibility, preventing Zed's autoattack execute damage from landing, nor Duskblade.
Zed can use Ignite, but that doesn't let him target her with autoattacks.
Zed either has to back off or suffer Vayne's wrath of AT LEAST 3 autos equaling her AD x 3, any BoTRK + Rageblade combo, a guaranteed 14% of target's maximum health, and BoTRK's onhit damage in exchange dealing R's initial proc damage, E damage, and 1 shuriken, Ignite, and R's pop damage. This looks like Zed gets a good tradeoff, but there's a key outlier, which is that Vayne and Zed will usually run Guardian Angel if they need survivability. Even if Zed gets a free Guardian Angel, his W and R are out of rotation by the time Vayne has come back to life, having to rely on his E and Q, and if Vayne can't kill Zed before the R pops onto her, then she hasn't reached her lategame potential and the loss is because of macro game, rather than micro game.
Again this is one of her worst 1v1 scenarios. The best is against someone like Cho'Gath with highly telegraphed abilities and easily kiteable.
What about Kai'sa? Kai'sa is ALSO a teamfighter, but admittedly functions a lot differently than Vayne, because her area of expertise is not limited to 1v1s. Her area of expertise is AoE damage, and this is the edge she has over other late game carries. How does she AoE? Through her Q, but primarily through her passive's interaction with Runaan's Hurricane and Guinsoo's Rageblade.
Kai'sa excels at general backline fighting + threat plays. You don't know when a Kai'sa will use her attack steroid. You don't know when she'll add an extra 473 (+150.5% bonus AD) physical damage to you while autoattacking. You don't know when she'll suddenly launch a W through the Fog of War, and you don't know when she'll use her Ult and gain repositioning + a massive shield, but even without these, her autos will whittle down up to 3 members of your team at a time.
Both ADCs do not have horrendously long range, and so utilize their abilities for a strict advantage that allows them to have multiple tools in their disposal at any given point. Vayne basically has a faster Tristana ult on her E, and Kai'sa has a mini Vayne ult+Q on her E.
I was a Vayne main until I decided to try some other champs. After my experience with Vayne and Kai'sa, let me explain the kit differences between them.
General Mobility:
Vayne uses short dashes rather than short movement speed boosts on a lower cooldown to amplify damage in tiny bursts and to reset autos to shred tanks. Gains bonus movement speed towards enemy champions.
Kai'sa uses a movement speed boost for a short while that resets 0.5 second cooldowns on autoattacks.
Stack Damage
Vayne's W is fixed. Kai'sa's Passive is not, and scales with missing Health. This difference isn't actually that large except for its interaction with Guinsoo's Rageblade and Runaan's Hurricane, where Kai'sa gains a TON of AoE damage from it
Stealth
Kai'sa's invisibility is available through her E, so she can use it multiple times in a teamfight, right after having skirmishes. Each autoattack reduces the cooldown on her E by 0.5 seconds, so expect her to be able to use this every 7 seconds or so assuming she autoattacks for 3/4 of the time it's on cooldown. She only gets invisibility for 0.5 seconds though, and can't auto attack during this time. Note: The stealth increases her movement speed too, so she actually gets more distance than you would expect.
Vayne's invisibility is basically on a 3 second cooldown due to 1.8 second CD on Q and 1 second of stealth, with 1 second of that being invisibility. It is only available during her Ult.
Self Peel:
Kai'sa doesn't actually have any, but can sometimes escape through her R.
Vayne's E. Bonus if you land against a wall.
Repositioning Power During Teamfights:
Kai'Sa can R to any enemy champion that has been auto'd, Runaan'd, or CC'd by a friendly champion. Her E also allows for slight repositioning.
Vayne can Q rapidly in short dashes.
Poke and Follow Up:
Kai'sa can W from miles away, and can follow up with an R.
Vayne can Q auto E and follow up with Ult if they hit a wall.
These are all things that make a hypercarry good, but Kai'sa has so much more range than Vayne that she can work with that her power doesn't entirely come from her base kit's damage, which is different in functionality from Vayne, but rather comes from the Range and Threat that she can use.
