Make the first sentence usable
Lead with the reason for writing so the recipient does not have to decode a long emotional introduction. For a message about how to address unhealthy competition with a friend, use this factual base: use one or two recent examples and name the trust, effort, money, or inclusion issue they created.
Reduce the work of responding
Offer simple options, a narrow question, or a clear update that can be understood without another conversation. Ask how your friend understood the situation and propose one change that can be tested. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Respect the boundary already visible
Do not assemble mutual friends, post indirect messages, or use confidential information as evidence. Stop direct contact and use appropriate support when there are threats, stalking, coercion, or safety concerns. A block, explicit refusal, legal restriction, or safety plan takes priority over the desire to explain more.