I know if a speaker address another character by their name directly it should have commas around it. But what if they used the pronoun you instead. Such as, "You leave her alone!" Should there be a comma after "you"?
I don't think it matters, but the "meaning"/tone changes a bit if you have a comma or if you don't have a comma.
No comma in this situation.
The sentence is a command, an order:
"You leave here alone!"
The speaker is not addressing a person by name; he's using a personal pronoun.
If the speaker were addressing a person by name, as in:
"John, leave her alone!", that's different.
If you're talking directly to someone as in, "Ted, what do you think of this?", then, yes, you'd put a comma there.