Akali Counter Tips
Don't let her use Mark of the Assisin on you(her Q) after level 6 since she can instantly dash forward and reactivate it to deal even more dmg.
In teamfights and ganks always try to carry a pink ward in order to disable her shroud so that she will be unable to hide under it.
AOE type of abillities will deal damage to Akali even she is stealth under her shroud.
Harash and poke her till level 6 because basically she is useless without her ultimate and if you keep your distance there is nothing she can do.
When playing versus her on other the mid roles, picking some champions that can take lots of damage will save you from a lot of trouble since Akali is specially made to kill the squishie low hp champs.