The reply you write while angry is usually the draft. Let it sit twenty minutes and see if you still want to send it.

Anger writes quickly and confidently, and it is a poor judge of what future you will want to have said. The message feels perfect in the ten minutes it takes to compose, then reads differently by morning. Nothing is lost by letting it sit, because if it is true at nine tonight it will still be true tomorrow.

Write the whole thing, then put the phone down and go do something else for twenty minutes. Come back and read it as if someone sent it to you. Send what survives that, which is usually about half.