The critical fact here is the basis for the harassment by the other employee. Personal dislike and animosity? Gender or racial discrimination? The fact is that your employer had a legal obligation to affirmatively act to prevent and end all harassment only if the harassment was based on grounds that are prohibited by law -- primarily race, gender, national origin, religion, etc. If the harassment was based instead on personal animosity and dislike, competitiveness, or that employee's bad character and personality, rather than legally prohibited bias, then your employer had no legal duty to act to stop or prevent harassment unless the actions rose to the level of criminal conduct or constituted a risk of workplace injury.
Your case is also complicated by the fact that by your own statement, there were problems with your job performance. You were either an at will employee or represented by a union. If you had a union, reach out to your union rep for assistance in determining your rights to appeal your termination.
If you had no union, then your employer had a lawful right to terminate you for any reason not prohibited by law. Tardiness, failure to get along with others, or any of the grounds on which you were previously suspended would all be legally sufficient reasons for terminating you.
All that said, 12 years is a big investment for both you and the employer. That fact alone makes it worth your time and effort to arrange a consultation with a local employment attorney to discuss whether you have any sound remedies here. Consider not only legal remedies, but also whether an appeal to the employer might have some potential for a change of heart.
Best wishes for a satisfactory resolution.
My responses to questions on Avvo are never intended as legal advice and must not be relied upon as legal advice. I give legal advice only in the course of an attorney-client relationship. Exchange of information through Avvo's Questions forum does not establish an attorney-client relationship with me. That relationship is established only by individual consultation and execution of a written agreement for legal services.
Like most employment law issues, it comes down to the facts and these forums are not sufficient enough to full address potential issues. Feel free to telephone my office to go over your situation to better assess whether you have a case.
Not sure how to take your comments about getting into trouble at work. You will need to be clear about this when you talk to the attorney.
The above is not intended as legal advice. The response does not constitute the creation of an attorney client relationship as this forum does not provide for a confidential communication.