Critical Yi is the only Yi, Ad yi and AP Yi have nothing on him. Critical Yi will demolish through everything you hate and love. There will be a number of different topics that will be discussed throughout this guide of Critical Yi.

Some things that will be included in this Guide are:

Why Critical yi?

Is he really that good?

Should i be worried that Critical Yi is this squishy?

How much damage do you expect out of Critical Yi?

Some things that wont be in this guide

Which is the best, Jungle Yi, A.P Yi, A.D Yi or BADASS CRITICAL MASTER YI

How to counter another Crit Yi

What came first, the chicken or the egg?

The best ever build for Master Yi

Believe or not, I have not finished this guide for Critical Master Yi, I am far from it. Once I finally start snowballing in a steady rhythm of guide fixes and just the general shine and polish, feel free to hate on me and leave a comment on different ways I can improve this guide

Pros

+Has the most amazing damage output, and a pro Master Yi will dominate the game

+has a varied set of skills that are all amazing

+A self sustain in lane

+Easily the most feared champion for any adc

Cons

-so squishy that some supports threaten Master Yi

-Even a small stun will ruin Master Yi

- focused down, A LOT

- Very mana hungry when on a roll

Shiv Yi is one of the most squishiest things you will find getting kills in the league. With Shiv yi just having just under 2000 health even with a full Build can make you very easy to burst down With little effort and having Something stun you for example a Morganna or Ryze skillcast, it can pretty much destroy you. BUT, while being squishy you have the most amazing damage outputs in the game, making Shiv Yi, The definition of "Assassin". His low health and squishy-ness is a no no but his damage, Critical damage and attack speed, all with a healthy dose of movement speed and lifesteal makes Shiv Yi a very dangerous enemy. Shiv Yi will often be targeted in any fight and will consistently be able to burst down the enemy teams ADC before they can position themselves. Shiv Yi must be able to bait, Unless your incredibly lucky or confident as Shiv Yi, the best thing you can do is either 1 v 1 everyone you see, Or get a team mate to tank the skill shots, allowing you a very quick Double or Triple.

Sustain Critical Master Yi is for those who are new and cannot plan when to charge in for a quick triple or run away LIKE A BOSS. The build associated with this version of Sustain Critical Master Yi, allows early game sustain against another top lane like Critplank. The reason why Critical Sustain Yi must start with the frozen mallet is for Sustain and to make sure anyone you touch then becomes your *****. With the added health and passive, it becomes a great ***est to Critical Master Yi. The Banshee veil is there to protect the new players and cannot dodge a stun. This allows Master Yi to charge into battle without worrying about any stuns. Sustain Critical Yi is as well a dangerous oppenent to lane against but his damage output and speed are nothing compared to Shiv Yi.
This is a slightly more tankier build for Master Yi with still a healthy amount of Badass and mobility. Sustain critical should be a must before you try out Shiv Yi to understand what type of pressure you face in battle knowing a single stun can end you and you're always stuck between a rock and a hard PENTAKILL.

I wont go within great detail with the runes because they are extremely easy to understand why the would be in a Critical yi build. 3 lifesteal, cause you are a badass and you have very little lifesteal early or mid game. these Runes should help you stay in lane as well as secure those extra kills. Armor and Health regeneration because you still need that extra little bit of tankiness. Critical chance(at early game it will have a great deal of effect) because Overkill, isn't over-rated. and lastly some gold for that extra farm and speed to finish your build, they faster you go through your build, the more dangerous you will become. A good farm can leave your oppenents surrending at 20.

Badass Yi has some pretty badass skills, but what makes Master Yi incredibly unique is the versitility of these skills, you got the Q for jungle Yi or A.P yi, you have an e for badass Critical Yi, or A.D Yi, and a W for the extra sustain or a shield for A.P Yi. Master Yi's first skill Alpha Strike is great if timed right, with this Master Yi can dodge A LOT of Skillshots that have been thrown at you, even ultimates if you time it right. Master Yi's W, Meditate is great once youve killed someone, about to die and have been ignited. This W will help you tank through all of it or even a minion wave if you've been caught in a bad position. Master yi's E, Wuju Style is the bread and butter of your critical Yi build A well timed E is devasting and will destroy through all Adc's and everything that you can see, only Baron can define your reign. Lastly, Master Yi's ultimate is the most mana consuming thing you will ever come across when your racking up kills(HighLander) This will make your Critical Master Yi a BADASS CRITICAL MASTER Yi, combine this with a good E and you will always come out on top for any 1 v 1 you have in the jungle.