His scaling is unparalleled and he does really well in duels due to his E and Q. The longer the game goes, the more dangerous he gets and can practically kill anyone no matter how healthy they are.
The E makes him take less damage from AoE abilities. This is really beneficial for him during full-blown team fights. Besides, the E CC also acts as a really good initiation tool for his team.
His Passive allows him to split push relentlessly. This can be extremely useful when Jax’s team is behind and can’t win a fair team fight. His Q allows him to escape collapse attempts with ease.
He is really weak against single target CC. During a team fight, if he happens to get chain CC’d, he will die before he can achieve something significant.
The enemy can always react to Jax’s plays and send someone from their team to prevent him from split pushing. They can even kill his entire team and then go for crucial objectives like the Baron.
Weak against champions who are ranged and can kite him out of his Q range. This allows the enemy to poke him out and then all-in him once he has been whittled down.
0 - 15 min
Jax needs time to come online. While he can trade in the early game, it’s better to get a few levels behind you before looking for a kill.
Be prepared to scale if you’re in a tough matchup so you do not fall behind and become useless in the later parts of the game.
Keep the minion wave closer to your side of the map in tough matchups. Jax will find it really hard to survive the laning phase if he is constantly pushing.
15 - 25 min
After the laning phase has ended, go to a different lane (or stay top) and just split push. You’re a good split pusher and can draw a lot of attention to your lane.
If somebody tries to contest your split push, look to fight them. Jax is a good duelist and will be able to fight most enemies who try to stop him.
While you’re a champion that is usually sent to split push, you might need to group with your team if the enemy is trying to force something. Be prepared to rotate around the map and help them fight.
In the late game, continue to split push if your team isn’t at risk of dying or getting caught out.
If your team is going to get caught out or if the game isn’t one-sided, you need to group with your team to help them fight.
Play on the side of the map that has the next major objective up so you can rotate to take it with your team. Alternatively, if you have Teleport, you can go to the bot side of the map and use it to get to your team.
Jax's first item component allows him to chase down enemies during an extended fight. It will let him stack up his Passive and completely decimate his enemies. Going for regular short burst trades using the lane brushes will help him a lot.
Level 6 is a decent power spike as it will increase his survivability during fights. Once he gets more items, this ability will help him kill enemies with ease, and he can take over the game with his scaling.
Jax isn't very strong early on as he is quite item reliant. He should be focusing on farming and short skirmishes to clean up kills. Neutral objective fights are situations where he can capitalize on this objective. He should also be using the lane brushes to go for short burst trades in the lane.
Jax's W being maxed out at level nine is a superpower spike for him. He can take frequent fights and take little to no damage. In addition, the CC aspect will allow him to score many picks throughout the game.
His mid-game is not as weak as his early game because he will have his core items and can use his Passive pretty well. He will also be a part of many objective fights, allowing him to land a multi-man W stun on the enemies. His W can also be used to make cheeky plays using the lane brushes and lack of vision.
Once he gets two points in his Ultimate R, he will become mighty during team fights. This is because his survivability will increase, which will increase the amount of consistent damage dealt by him with his auto-attacks.
His Q being maxed at level 13 will give him a massive power boost, and he will be able to win duels with ease from now on. Jax should try to split push and duel anyone if he isn't too far behind.
Jax's main spike comes when he reaches the late game and has multiple items in his inventory. Now he can actually 1 v 5 against the enemy team and come out on top. He can play a mind game and see if he can catch the enemy carrying farming in the side lane. The brushes in the Jungle are great spots to hide in to achieve this goal.
Since Jax can deal a lot of consistent DPS and is heavily item reliant, he will be mighty once full build. He should get a defensive item, though, as he needs to survive to actually deal the damage.