I believe he'd still be able to control people even if they don't understand English. His body produces chemical pheromones that have to be inhaled or absorbed through the skin, which is why he can control people, so I don't think it would matter either way??
I’ve thought about it some more, and I really do think he can only control people who understand him verbally, because (spoilers under cut):
1) In the finale, Trish wears headphones and plays loud music to block out his voice. It works, which must mean she has to hear and understand his commands in order for him to control her.
2) There are several examples where his words can be twisted to mean different things. When Kilgrave tells Jessica to get rid of Reba, Jessica does exactly what he wants because she understands “take care of her” = “kill her”. That seemed to indicate that as long as his intent was clear, the command was unbreakable, even when issued metaphorically. But later on when he orders Trish to put a bullet in her head, Jessica resolves it by putting the bullet into Trish’s mouth instead… which means you can get around his commands by interpreting the *actual* language he uses. And you can only interpret language if you understand it, right?
