This is a build i've made for Tryndamere to get the maximum armor penetration without losing on the critical strike stuff and it has been quite successfull ever since i've started using it.

+ Tons of damage. - Quite squishy if focused too hard
+ Balance between
armor pen, critical
chance and damage.

I really like flash but you can take ghost istead but cleanse is a must since you are gonna be getting exhausted into hell by the enemy team.

Passive - Battle Fury - This is one of Tryndamere's main steroid as well as a form os sustain through his Q, at full rage bar tryndamere gets 35% critical strike chance.

Q - Bloodlust - This is Tryndamere's second steroid, it gives him ad for every percentage of hp missing as well as a flat bonus ad, on activation however you consume all your rage to get some hp back depending on how much rage was consumed. Do not activate it unless it's totally necessary because you will lose your bonus critical strike chance from the rage.

W - Mocking Shout - This skill decreases the ad of nearby enemy champions by a lot so be sure to activate it when you are trading harass, if the enemy has his back turned he is also slowed so it's an awesome chasing skill.

E - Spinning Slash - This ability is what makes Tryndamere so mobile, with it you can pass through walls, creeps, champions, etc, and it has it's cool-down reduced by 2 seconds every time you crit so it's your bread and butter escape/chasing ability, use it wisely.

R - Undying Rage - This is Tryndamere's "signature move", it lets Tryndamere live with 1 hp for 5 seconds and fills up his rage bar depending on the level, use it when you think you are gonna die (obviously).

Farm as much as possible and only trade with your lane opponent if you know you can out-sustain him with your Q or your pots or if you know you are gonna come out ahead, go back as soon as you can purchase wrigles and lvl 1 boots. always ward your lane with your wrigles. IMPORTANT: Never miss a last hitting to harass without a reason.

Continue farming up, when you get strong enough you can look forward to picking fights with your lane opponent or just deny him if you are ahead. Ask your jungler if you can take some of his creeps when your lane is pushed to the enemy tower.

Once you have all or most of your items you should be dealing an ***-load of damage so try to focus down the enemy's squishys without getting focused yourself. if the enemy has a Lux or a LeBlanc or some squishy champion of sorts you will be finding yourself 3 shooting them with all of your items with ease, it's actually quite funny.

That's pretty much it, it's my first Guide/Build and i'm Brazilian so my English is quite bad so don't be too harsh on me.

With the full build you get 110 armor pen if you count all the stacks on the BC so that's a lot of armor pen for you to wreck with.