DISCLAIMER: It is an unusual build. You may get spammed by meta sheep. Show them what you can do! Maybe you will teach them to be more tolerant ;-)

Welcome to my Crithresh build. I thought it up long time ago, but I was afraid that too many people will play it and Riot will nerf it. The thing is, I am not exactly good with ADC characters and cannot use its full potential. So there you have it: a build, that allows you to deal about 2500 damage in one hit (before being reduced by armor and MR by armor and MR). Interested? Than read on! :D]

Don't look at the stats section, it's all messed up, because 1. I use build order as references 2. Mobafire doesn't count Souls (obviously) and 3. It also doesn't count Bloodthirster stacks.

Also, I know it isn't pretty. I'm bad at making things pretty. Deal with it. Maybe I'll try in the future to make it better looking. Sorry about the walls of text, I can assure you they're worth reading xD

Advantages:
-Insane damage. You can actually oneshot most squishies without even a full build. The look on your enemy's face, when you suddenly appear out of a bush and one-hit-kill him is priceless.
-Actually balanced proportions between one hit dmg and attack speed. Even if you fail to oneshot your target, you will most likely still get him with few more autoaattacks, since they still deal the 300% of your AD.
Disadvantages:
-Kinda squishy, like most adcs. In the most cases you will not be able to use your Q dash just because if you get focused, you die. People, who have played offtank Thresh will have to change their habits a bit ;-)
-Not realy meta build, you may get some hate from your dumb teammates. Well, **** happens.

All hail critdamage! Not much to explain there. This setup usually gives some trouble in very early game (you practically have no runes until you get a decent crit chance), but Thresh is very strong in this phase. Stay clear of Teemos and Malphites and you'll do ok.

This is supposed to be top build, so there's not much choice with partners. Thresh works great with high damage junglers - your enemy's worst nightmare is Tryndamere, Lee Sin or Fiddlesticks suddenly appearing while he's being pulled. :D And this is only a small tip, practically any jungler will do. Now, to opponents:

Bad for you:
- Teemo Your worst nightmare, an ideal counterpick. Pokes, blinds and doesn't care about your armour. Your only chance is poking him with full E while not blinded and comboing him under your turret. You may want to ask your jungler to camp top.
- Malphite Rock solid. This OP **** just DOESN'T DIE. He will endure everything you and your turret will throw against him and will poke you all the time. The only way to win this lane ot to poke like hell.
- Garen Also immensely hard to kill. Your only chance is not allowing him to ever get near you and poking all the time.
- Quinn This.. I don't even... Seriously, what did Riot think while making this champ? She will outpoke EVERYTHING, including you. Sit under tower, farm, catch souls with your lantern and wait for ganks.
-basically everything that is immensely hard to kill and you do not want to pull, or pokes you more than you poke it. :D

Good for you:
- Lee Sin Deals mainly physical damage, at the start ideally countered by Thresh's passive. Just evade all de Q's, poke all the time, and give him QEWR combo each time he tries to dive you.
- Riven Same as lee sin, countered by your passive and cc's. If she gets too close, you can always pull her under turret or E her away.
- Heimerdinger Yes, he can go top. Why not? I have met some. The thing is, if you get Statikk Shiv, evade his granade and aa him a few times, he''ll just die.
- Master Yi HATES YOU. He can stick his insane damage up his arse when he's stunned and pushed out of range. Also in late game you can either oneshot him before he Qs, or nearly oneshot him, wait till he appears, Flay him away and finish the job with one more strike.
-basically everything that is squishy and/or ad. Ergo, he is awesome on top.

Additional tips:
-while facing Gangplank rush a Vampiric Scepter right after Alvarice Blade. Those items will allow you to nearly negate his farming and healing advantage. Also keep in mind, that you have cc advantage over him and can continue attacking from a distance after the first hit.
- Vi is a tricky one, if she know how to play, she will certainly mean some trouble. Dodge her abilities every time you can. There's an useful trick with your E, if you time it correctly, you can stop her Q while in flight.

This item set was created to balance first hit damage and DPS (for new players, it means Damage Per Second). If you feel confident and have whole build, you can exchange Stattik Shiv for another Bloodthirster and, finally, Berserker's for a second PD. With this setup you are a bit slower, but you can deal the 2500 onehit damage I was talking about. You can also get Last Whisper instead of that last Bloodthirster, it will increase your physical damage output and DPS, but I prefer first option, for sheer power not only as AD but also from your Flay passive.

Explanation: You will have approx 500 ad. You will deal 300% of your ad on crit and max. 200% ad from your Flay passive. 500 ad x 500% = 2500 dmg (1000 magical and 1500 physical). There, of course some of it is lost to armor and MR, but it still is enough to oneshot nearly any champion wthout additional hp items.

There is also the Critplank build, which grants you 100% crit chance and only a bit less AD, but it butchers your DPS. In other words, after one shot your damage compared to normal build is hilariously bad, but it allows you to crit without fail on the important first strike. I never really build it.

Your basic offense heavy masteries tree, maximizing your damage in any way it can. I even include the Double-Edged Sword , because any damage multiplier is good.

Simple. Max E first, than Q, than W and obviously your ult every time you can (on 6, 11 and 16 levels). Though, you need to get your all skills as fast as you can, since they all are very useful. Flay grants you damage and an usefull CC, Death Sentence grants you one of my favourite ccs in the game and a dash after running opponent and your Dark Passage makes it easier to collect souls and helps with ganks if your jungler is not that mobile or stupid. one thing: It's completely and utterly useless as a shield. It's shield delay is too long, shielded amount is too small etc. It can help if enemies tower dive you, and that's it.

Most of you already know how important farming is, but in case there's some relatively new people, I'll explain: landing a last hit on a minion grants you gold. You may not thing it's a good amount of gold until you realise that about 6 minions = 100 gold. Yup. Incredibly important. Your Flay passive will help you immensely with farming.

If enemies have a jungler (and if you're playing on at least decent level, they most certainly will), try not to hit minions asides from last hits. If you do this, you push your lane under enemy's turret, making it harder for you to harass him, easier for him to harass you and it makes you vulnerable to ganks. According to the same rule, if you don't push your lane, and enemy does, all the above apply to him.

Also, there's a thing I was surprised to see how many people not know: Farming under tower. You need to remember that the tower takes two hits to lower a melee creep to ideal last hit HP and one hit to lower ranged creep to pretty good last hit hp. So, under tower you SHOULDN'T hit melee creeps at all asides from the last hit and depending on your damage you should either hit a ranged creep when the tower is aiming at it, wait for tower hit and hit it one more time if you have low damage, or just wait for tower hit and then land last hit if you have higher damage.

You should play thresh like a bursty ADC such as Draven or Sivir.

EARLY GAME:
As you have pretty much no benefit from runes in early game, you'll have to play a bit defensively. If you get into trade, you'll lose it. That means your early game consists of farming, poking a bit with your enchanced autoattack, some more farming, defending under tower, even more farming... You get where I'm going xD Thankfully, Thresh is really strong in early, so you shouldn't have any problem with that. The rest about early game is about tower dives. You'll have many cocky enemies trying to dive you, especially if they're playing with nobrain champions like Xin, Riven, Darius, Aatrox or Renekton. The standard tower dive procedure goes like this: wait for the tower to focus them, either if they're attacking without minions or they hit you. Q them. This is the most important part, they will expect this, so they will quite likely try to dodge it using dashes or means of invulnerability like Maokai's Twisted Advance, Master Yi's Alpha Strike or Fizz's Playful / Trickster. You need to make sure they have already used it and can't escape your Death Sentence. DO NOT press your Q again, not only will it dash you to enemy, which is exactly what you want to avoid, but it will also prematurely end the duration of the stun/pull. If you did it correctly, it grants you few free tower hits. Now, either your enemy will decide he'd rather back off, or will continue the dive. In the first option, Flay him closer to you and autoattack the **** out of him, use The Box if you're pretty sure it'll grant you the kill. In the second option, toss your Dark Passage on your position for delayed shield and autoattack until he comes into melee range, then use The Box and Flay him into it, away from you. Even if he manages to score the kill, he'll most likely die from the tower, resulting in kill trade, for your advantage. Why? Because you're a late game Crithresh, with every piece of gold getting closer to oneshotting people. A kill trade is exactly what they DO NOT want xD Keep in mind tho that kill trades are a bad thing overall, and if you have the choice of not dying and not scoring a kill, or dying and getting it, always choose to not die.

MID GAME/LATE GAME OUT OF TEAMFIGHTS:
Out of teamfights you can pretty easily 1v1 anyone that isn't way more fed than you. There are two ways to behave depending if your enemy is melee or ranged. If he's ranged, Use your Death Sentence, wait a moment while it pulls him, press Q again to dash, then proceed to autoattack him until he dies (which won't be too long xD), keeping him in short distance with E if he tries to run. You can eventually use The Box to stop him from running, but use it wisely since it has pretty long cooldown. Another thing is with melee champion, which you will try to keep away from you, so you won't use your Q dash, only the stun, you'll use Flay to push him away, not closer and, eventually, The Box, if you REALLY don't want him getting near.

TEAMFIGHTS:
Your teamfight contribution is to walk into already begun temfight after the heaviest ccs and combos are already used, hit the enemy dealing the most damage (usually their ADC), and continue to focus him untill he dies, then move on to second most damage dealing enemy etc. Your Q should be used in teamfights only if you can hit a squishie that your team can finish off, because if you hit a tank, you waste precious time while pulling him and not being able to autoattack. As you won't be in the middle of a teamfight, your R won't be so useful unless some melee champion focuses you or your enemies are running and you dash to them with Death Sentence and then ult to stop them.

So, I think that's about all I wanted to show you. If I forgot about something, please let me know, I'll check Mobafire once in a while. Constructive criticism is welcomed, while comments like "omg you are so noob Thresh is an offtank duhbuh" can be sticken up your arse. I hope I helped you with this guide, I may do few more unusual build guides if I ever feel like it.

Credits:
jhoijhoi, for the Guide to Making a Guide. It helped me a long time ago, when I was making my first guide.