Is there any channel for us to complain when we are bullied by a moderator? I really hope that Stack Overflow can be a place which is fully transparant. If we were being bullied by a moderator, the evidence should not be wiped off (edited or deleted) by the big bully (moderator). Also, I hope there is a tool for us to vote on the moderator that likes bullying so that everyone knows about his real face.
If you are talking about regular users with moderating privileges, you can flag for diamond mod (users with a ♦ next to their usernames) attention.
If you are talking about diamond moderators however, you can contact the team directly. Just click on the "Contact Us" link that you can find at the bottom of any page on the site.
As for "voting" on any user, moderator or not, because they engaged in inappropriate behaviour; that is not possible. Let those who can handle the situation. Don't start voting on users for any reason other than the quality of their contributions.