Ok lad , you seem upset because you probably got destroyed by one. Heres the thing about Jax, hes a hyper carry.... Now meaning his late game is very strong , to balance that out hes supposed to have a weak early game. But hes a champion that doesnt have a terrible early game , but he can duel early game. He has one of the strongest lvl 1's , but it becomes difficult after that. And as you said , he gets an item and he can 1v1 anyone. Not really , he needs items to scale , just like every other carry , but lets look at his items.
3733,
3500 ,
3200,
3000,
2800 , and boots which are 1100 (tabis or mercs). Jax is good early , but he gets harassed , kited , and most of the time out traded... Because early game what determines a champions strength are abilities , then LATE game are auto attacks. Jax relies mostly on his auto's early game , mid game and late game. And if you see his item set , you can CLEARLY see they are VERY expensive. Getting triforce , and following that up by titanic hydra can take a while , and a lot of champions spike before jax gets to his spike , so he gets bullied , and probably blown up because hes not tanky yet. There arent that many high elo Jax's for a reason , the champion is very simple and gets easily countered either by an over powered bruiser , ranged top laner , or a tank (unless you count the times , TF blade uses him but its rare). Plus if you want to make sure jax doesnt do anything all game or ANY bruiser doesnt have fun pick
, stupid base dmg , high armor and mr. She can shut down Jax without a problem. If you have such a problem with jax , you play and find out... See why every jax main isnt some high elo god that can 1v9.