good build

I good quesion. you can easily take FoN over Sunfire, but when dueling, Sunfire Aegis is absolutely Godly! but if they have really high burst, then FoN is a much more viable option.

Honestly, this is a great guide :)
But wait, i just don't understand the reason to take Sunfire Aegis..Don't you think that you should take Force of Nature instead? :\
Anyway 1+

I like the improved Lee :D

You're now ready for your +1 xD

Im glad you see ive improved, and yes, i can easily trade Youmuu's Ghostblade with another item like Sunfire Aegis or a Frozen Mallet

Hey =O your guide is absolutely shocking! Great improvements and really a job well done! However I have to say that Youmuu's Ghostblade isn't a great item on Lee Sin. It's decent but not extreme and late game isn't that good either. May probably want to remove it in place for either Sunfire Aegis which I find to be extremely powerful on him as well. Other then that, good job! Have you checked out my Swain guide yet? ;) *winks* lol jk, you can if you want. +rep for the great improvement =) gj bro

I find this guide would be of a helpful service to intermediate playes as it provides handy counselling over some of the core mechanics of Lee Sin although I do feel that it does need polishing up slightly for it to be completely refined (particularly the "Skill Sequence" section) coupled with some illustrations in the "Skills" chapter to be more user friendly.

Pros / Cons

Lee Sin has a strong early/mid game with his late game depending on how it went on earlier so having a strong late-game isn't strictly true. I'd also add hows hes an amazing duelist which makes him both resilient to counter-jungling and very capable at doing so.

Why The Blind Guy?

His early ganking ability is indeed strong can even "gank like a god" at level 2, I've had countless number of first bloods from a level 2 gank which usually people don't see coming thus adding to the element of surprise.

Runes

Why would you think that attack speed is fairly weak on him? Flurry suffices enough (even after the nerf) which is up almost all the time. Greater Quintessence of Desolation is inferior to Greater Quintessence of Attack Damage due to ratios. Greater Glyph of Scaling Magic Resist should be noted for these wanting better defenses late-game.

Masteries

Ummm.. yeah you may unlock Executioner after spending 20 points in the offense tree granting you access to it but you still have to actually put a point in to it. So, just have to take out the point in Summoner's Insight .

Skills

Should note somewhere when describing Safeguard that it can be used on wards or ally objects like Noxious Trap. Also, when talking about Tempest more emphasis should be highlighted about its attack speed reduction and how inflicting this on an AD carry in team-fights has grand effects particularly if that AD carry is attack speed reliant in someway such as Vanye with her Silver Bolts.

Skill Sequence

Yeah, you've been saying how Lee Sin is a great ganker and has strong early ganking potential etc but leveling in this way just gimps your damage early on - the reason Lee Sin ganks pre-level 6 are strong is due to Sonic Wave / Resonating Strike damage then the snare. Just seems a waste to put it in second place priority, try it out with first place priority (before ultimate of course) you should notice a substantial difference. Not starting Tempest slows down your jungle drastically as well.

Summoner Spells

I'd include Exhaust as an option as its very much viable and used by many players due to Lee Sin almost having an inbuilt flash with Safeguard.

Items

Youmuu's Ghostblade is a fairly sub-par item late-game, at that phase of the game people generally have a chunk of armor and Youmuu's Ghostblade offers little ARP so not much point doing extra damage just to be mitigated by armor. Either Last Whisper or Black Cleaver prove to be more effective at that stage of the game depending on the enemies armor rate.

Jungling

You should include alternative routes in case one gets invaded for instance or wishes to try for a early gank as such start red. You can clear wolves before blue spawns but only if you pick up Tempest first thus another downside in picking Safeguard first.

Just fixed it

I personally prefer safuguard due to the lifesteal, and last time i checked my masteries. 20-9-1 worked since you unlock Executioner when you REACH 20 Points

The only thing i can comment on in a bad way is that 20.9.1 are not possible since you need atleast 21 points in offense for executioner

But maybe you could include some more optional items since i know there's other good choices and tempest/cripple will give you an faster start :)

Please do tell me if you like it or not, i hate troll downvotes -.-