Leblanc vs Annie-
Leblanc is an early/mid game mage assassin with high burst, with low farm skills. She can chain silence someone for up to...6 seconds iirc, or (if they're good) silence two people for 2 seconds each. She is good at downing one squishy/carry every 15-30 seconds depending on AP/CD/her target/MPen/skill. Her hard counter is not getting fed early game since she can't farm well, but if she is fed it takes a lot to shut her back down assuming she does her job right of either plucking 1 off at the start and running back, or downing 1-2 stragglers from a team fight.
Annie is a short CD mage, with a defensive spell, a tank/burst Ult, and a CC that is up very quickly, and very often. She is often used for burst damage at a start of a fight, and then plucks off one single/two targets as her CD's come back up. Her hard counter is ganks since outside of flash she has no escape (her stun can be used, but in a gank I'd assume more than one target/one to have a CC of their own). She's a general threat throughout the entire match unless she's kept down hard.
That being said, its kinda hard to properly compare the two considering the fact that their main job is different. If a Leblanc is trying to carry a TEAMfight, she better either be fed, a top tier championship player, or you might as well just let her die. If Annie does the same she most likely will get a decent number of kills/assists, while not falling over as fast considering her hard CC/AoE as opposed to Leblancs Silence and 1(maybe 2) roots and 1 AoE Spell that is usually used as an escape.