Leblanc is an early game bully. Watch out for her QW AA combo.
Whenever Leblanc’s W is on cooldown, she is squisher and vulnerable. You could use this time frame to play aggressive and go for a trade as she will not be able to escape or trade as effectively back with you.
Standing outside of the minion wave and far back is a good way to reduce Leblanc’s ability to push and poke at the same time with her W. If you stand as far back as you can, she will be unable to land her W on you regardless.
LeBlanc is an Assassin. That means if she gets ahead of the early game, she can snowball really hard and stomp the game. Do not overextend or trade aggressively when you know that she can kill you.
Make sure stay grouped with your team and avoid walking through unwarded areas of the map when you don’t know where Leblanc is. As she is is an Assassin, she can easily burst you down if you’re caught out of position.
To counter Leblanc in team fights, you need to CC her as soon as she uses her W. Once she is on your team, CC her immediately and focus all your efforts to take her down while she is CC’d.
Leblanc can go for bursty trades in the early game as soon as she unlocks her Q and W. She can also proc Electrocute very easily with her QW AA combo.
Once Leblanc hit’s level 6, her kill pressure intensifies as her Ultimate R is very versatile. It also has a very short cooldown, so play respectfully.
Leblanc is very strong in the mid-game once she has lots of AP and items. Make sure you group with your team so she cannot burst anyone down quickly.