Is this email too aggressive?
If you're asking, you already know. Here's exactly how bad it is.
Example situation
“Hey — I sent the invoice three weeks ago and still no payment. If this isn't resolved by Friday I'm escalating to your director. This is unprofessional and I won't tolerate it.”
Judgment —
Yes. Too aggressive.
Reality —
The deadline is fine. The escalation threat isn't. You jumped from "please pay" to "I'll go over your head" in one email with no middle step. That's not firm — it's hostile. The person reading this will remember the threat, not the invoice. You just turned a billing dispute into a relationship problem. The line about "unprofessional" is projection — you're the one writing angry emails at 11pm.
Cost —
You'll probably get paid faster. You'll definitely lose this client's goodwill. They'll pay the invoice and never hire you again. If they forward this to anyone else at the company, your reputation shrinks by one room. Net result: one invoice collected, one relationship destroyed, one door closed you didn't even know was open.
Real OneShot output — 1 input, 1 answer, no comfort