How do you not know that?  Your negative tag is due to an alt account with ban evasion.

You have a reference to a thread with more information: https://bitcointalk.org/index.php?topic=5270480.0


You cannot remove it.  The only one who can remove it is the member who gave you the negative tag.  It would probably be best if you create a topic in the Reputation board or contact that member privately.