Fiora

Fiora is very difficult because you can't really trade vs her at all, and she outscales you so it sucks. Also she can riposte 3 of your 4 abilities.

Illaoi

Illaoi outtrades you at all points in the lane, dominates side. And you can't punish her as maokai. But she's not very popular so only worth a ban if you saw illaoi last lobby. Just dodge the matchup nobody plays her.

Aatrox

Aatrox is generally a difficult matchup and he outscales you. Soo its a bit difficult. Also its hard for you to kill him and his fighting style is very good into maokai in lategame teamfights too.