Check the sticky post about rules concerning this:

!fediverse@lemmy.world is not a place to file your grievances with “free speech”, disrupting users, moderation, etc.

If you have problems with users: File complaints to the mods or just block them.

If you have problems with mods: File complaints with admins of the instance or just migrate to an alternative community.

If you have problems with an entire instance: Just leave it.

And to add: If you do want/need to highlight misbehaviour, stalking or even just rant about injustices happening publicly, there are places like !fediverselore@lemmy.ca (rules prohibit stuff you are personally involved in, though) and !yepowertrippinbastards@lemmy.dbzer0.com where it concerns mod/admin abuse.