Headcanon on Vox's hypnosis abilities:
I think it only works (effectively) when he has his intended target's FULL attention. When his audience is locked in to a show. When the press is hanging off his every word. When no one else is in the room and he's approaching you with that shark grin because he's the riptide that will pull you under. When his full attention is completely fixed on gaining control, or he's trying to get control over his target/opponent/enviroment.
which is why I think Vox tried to hypnotize Al after their Totally Not A Breakup at the bar that night. Al said he threw a tantrum and if we infer that to mean a fight, in which Al "put him in his place" aka won that fight, what would be the last ditch effort for Vox to try and regain control? For him to even survive a deadly encounter with The Radio Demon himself?
But it doesn't work. Al was too strong/broke free but it was enough for Vox to escape, and enough circumstantial proof for Al to cement the idea that Vox was only ever trying to use him.
Maybe afterwards Vox tries to apologize, tries to explain himself and that he was afraid and hurt and he didn't mean it because he knows Al values his autonomy above all else, but to Al: