Verb: to rule, to govern, to reign, to master, to control, to be in charge, etc.
Hallita appears in our example in the 3rd person singular, hallitsee.
Let’s translate the whole headline about Johnny Depp’s new movie Transcendence, ”Kuka hallitsee ketä,” or ”Who controls whom?”
Kuka means ”who.”
Ketä is partitive singular of ken which is an archaic or dialectical interrogative pronoun also meaning ”who.”