Jax is (in my oppinnion) not only the best twisted treeline champion, but also one of the best summoners rift champs. jax has the ability to stun and do sick damage, and with this build take exstreeme amounts of damage.

Early you must focus on staying alive and geting enought minnions and kills to get Guinnsos rageblade, if u get this item before lvl 6, u will mannage to take almost anny champion thanks to the stakg of passive, ulti and guinnsos. the focus after this is to get more damadge and life steal with hectec gunblade. if your teammates suck and have feeded the enemy, go shen, and bannish veil/sunnfire cape (depends what champ is feeded)

if u mannage to get feeded by 3-4 kills, u shuld have no problems even taking 2 enemy champions. the rageblade and hectec will devestate the ennemys. I have gone solo inn to 4-5 champs and taken penta, I was extremly feeded, but here is the atack order: use empower, and then leape on them. if the focus you use counter. go close and let the counter stun them. pop ulti and they wont be able to damage you. by the time the ulti has gone, u shuld have killd them and gottn counter back

the guinnsos and hectec is a must. i also higly recomend trinnity. if you wish you can change banshee and sunnfire to items that grant ad and ap. (but if u get sunnfire and bannshee you will have lots of hp and armor and magic ressist.) witch will make you able to solo any champion

Pros:
extremly tanky.
hitts a tonn.
moves fast.
can solo any champ Mid/lategame.
cons:
the most banned champ in twisted treeline.
recently nerfed.