Middlemen that bring up things that they did for you in the past
The worst kind of middlemen are people who will do business with you, or introduce you to a new client then hold you and your business hostage for a lifetime. They expect you to give them something free or at a steep discount for the tenure of your entire business. This is like doing business with a loan shark. You pay them back 20 times over. Whenever somebody does you a favor or something in business that helps your business send them a thank you card take them to lunch or do something to WRAP the situation that clearly indicates TIL NEXT TIME, but never allow the return of the favor to linger because you will NEVER stop paying the debt back.