CChairman:
I'm late to this, but just in case it's still is an issue, I have a few thoughts.
qwazse is right, the Charter Org Rep is the person that needs to get involved. While this may not be to their liking, it does fall under their jurisdiction.
Get a few parents to draft their list of incidents that the adult in question has done. Include dates, a brief description, and how it made them feel afterward. Having one list from you is okay, but three different perspectives hold more weight. Make a cover letter, as a leader, with the other reports, and send that to the COR. In the cover letter, tell the COR what you need them to do. (I guess it would be alright to print this thread and include it with your letter. At least the COR will have more confidence in taking action.)
Find the appropriate BSA pdf covering their bad actions. For example, I printed the 2019 Guide To Advancement, put that in a 3 ring binder, and showed that to a SM who delayed SM reviews. Having a guide in writing, helps a lot, but not always.
Now the bad news:
The #1 litmus for a bad scouter is that they get angry. When a volunteer gets angry, they're personally invested and have lost objectivity.
Getting them to change is unlikely, but not impossible. Don't let their anger affect you when you address them, remember it's personal for them.
Even though it is hard, it must be done. The longer they stay there angry, the more people will leave the unit. -In my experiences, I've found bad scouters to be undeveloped children; their bodies are old, but they think like an adolescent. I never disrespect them, BUT I speak firmly to them, giving them clear instructions on what they need to change, and I make them acknowledge what is expected of them. They have to promises to change the behavior. Give them a chance. If they don't change, or if they get worse, have the COR give their position to someone else. Also, be prepared to take on two roles at once just to keep the unit running.
NOTE: There is also a Unit Commissioner for your troop, but my luck with them have been hit (god like knowledge) or miss (another angry adult-child). Contact them vaguely, and see what they have to say. You can also reach out to the District Commissioner. Their email should be on the District homepage.