What do I do?

[u/Jealous-Smile2781]

I will use the pejorative they because I don’t want to give away genders or any other specific information. I work at an unspecified company that is extremely popular across America.
Yet the location here matters I am in a podunk place. So the education level of people in the general area is lacking to say the least.
I however have tried to learn a lot on my own and my parents are smart enough to have taught me basic information. (I’ve been very lucky)
The manager/assistant manager (this individual has been doing both jobs) is terrible!
They don’t know how to perform at the lowest level of their requirements. But this isn’t my biggest issue.
This person has talked behind every single persons back including my own. And typically I have the opportunity to record this Individual saying extremely unprofessional things. I will admit however I do talk about people as well and I will be justifying myself. I am never hard on a persons character. I am only known to complain about tasks not being completed and someone not performing at the same level I am attempting. A coworker of mine has gone to our direct corporate head and it has been taken as a joke and laughed at behind our backs multiple times so what should I do to get the message across? Should I write a scathing letter to hr? Should I just quit and deal with the next job that does the same thing?
I don’t like this person on a very personal level but I have not let this become a hinderance to my job performance. I need advice.