Jax vs Warwick

Start your trades with Counter Strike (E): you dodge autos and take less area damage, and each dodged auto adds damage to the stunning counterattack.

Look for long trades: each consecutive auto increases your attack speed thanks to Relentless Assault (passive).

To escape, place a ward and jump to it with Leap Strike (Q): it can target any unit or ward, allied or enemy.

Activate Grandmaster-at-Arms (R) up close: it only grants armor and magic resist if it hits a champion, and your bonus hits then land every other auto.

Keep your health above 50%: below that, Blood Hunt (W) gives him speed toward you and attack speed, three times more below 25%.

When he drops below 50% health, finish him fast, with CC if you have any: Eternal Hunger (passive) then heals him with each auto, three times more below 25%.

If you have a dash, don't count on it to escape his held bite: Jaws of the Beast (Q) makes him follow all your movement, then leap behind you.

In teamfights, stay behind your tankiest allies: Infinite Duress (R) suppresses the first champion hit, and its range grows with his move speed.

If you have Grievous Wounds, apply it to him: his autos heal him at low health, and Infinite Duress (R) heals him for all the damage it deals.