Write the angry reply, then leave it in your notes app until tomorrow. Tomorrow you is a better editor.

Anger is excellent at drafting and terrible at deciding. It supplies energy and precision about what hurt, and none of the judgment about what should actually be sent. A day does not soften your position, it removes the part of the sentence that was only there to wound.

Write it in full, because the writing itself discharges a great deal. Then park it somewhere it cannot be sent by accident. Read it back in the morning and keep whatever still seems true, which is usually about a third of it.