I like the fact that you included Rylai's Crystal Scepter in the build, but this guide still has a long way to go. I'll give you a couple of points I think you could improve on:

1. There is hardly any content. You fail to explain the majority of what's going on with the build, with no explanations for why you pick certain items in the build other than Rylai's, and you don't explain which items are important to swap out for others depending on the situation. It occurs again with runes, as you give a very brief glance at them, and again with matchups, where there are hardly any listed and no reasoning behind their placements. The guide feels very incomplete.

2. A lot of the information is inaccurate. For instance, Lethal Tempo is not the best keystone for Kai'Sa, while Fleet Footwork has a very high winrate comparatively, and Press the Attack allows for more damage overall. You also don't discuss any alternative or secondary runes. Taking W first is too risky for little payoff, as your Q at level 1 helps you clear the 3 minions in front when you're coming from a leash, so that you don't miss your lane pressure, exp, and gold, and also does a surprising amount of damage on an isolated champion for trading. W can be blocked by minions, has a large CD, and is fairly easy to dodge for the damage it does. I'd really recommend Q start in all situations, followed by E then W.

3. Following from the inaccuracy point, saying she has no bad matchups is just incorrect. Any champion that can CC her easily, poke her while abusing her short range, or all-in her quickly and early is a solid counter to Kai'Sa. Some examples would be Caitlyn, Ezreal, and Kog'Maw for poke, Draven, Vayne, and sometimes Kalista for all-in, and supports like Leona, Taric, and Nami for their CC and deceptively high damage.

4. This is a more minor point than the others, but adding visuals and color to the guide would improve it immensely after you add and amend information. Things like pictures of rune pages, videos for abilities, icons for items such as Mercurial Scimitar or , abilities and spells, and colored text for headings and subheadings would make the guide not only easier to read, but more enjoyable and helpful for the reader. The Wiki has an excellent guide to help you with this which can be found here: BBCode Guide

5. You spelled Kai'Sa wrong in the title :p

I'd be more than happy to come back and review the guide if and when it's updated and polished, but I thought for now some constructive criticism would be helpful. Wish you the best!