I am writing this letter to offer you my deepest apology and rectify my mistake. I am extremely remorseful for insulting you in front of our media team. I admit that my behavior was disrespectful and inappropriate in every way. This letter is not sufficient to justify my action, but I have not gathered enough courage to face you after that incident.
I don’t control why I started yelling and insulting you in presence of all staff members despite knowing that you were just trying to make your point clear during the annual sales conference on [date]. I want to let you know that my mental condition was not okay due to huge work pressure. Consequently, I could not control myself and it led to the occurrence of such a sad incident. Whatever I did was completely unintentional, and I was not expecting to use such words for you.
You have been a great mentor and I truly appreciate your kind support during my hard times. While insulting you, I totally forgot that you were the person who inducted me when nobody in the market was ready to hire me. I have realized that it was a huge mistake on my side, and I am extremely sorry for my inappropriate and disrespectful behavior.
I realized that I was wrong. Please give me another chance so that I would rectify my mistake and change my behavior. Please let me know anything that I could do to regain your trust.
Please forgive me and accept my apology from the core of your heart. I promise that I will not use such harsh words for you again in the future.

(Sample -2)
Subject: Apology letter for insulting
Dear Sir,
Before writing this letter, I decided to meet you in person but couldn’t gather enough courage to face you. I am in a state of embarrassment since the day when I insulted you in front of the whole staff member. You are a kind-hearted person and have been our mentor who is always ready to help other colleagues. I admit my mistake and accept that I have exploited your kindness by means of my rude behavior. Now I am extremely remorseful and consider myself accountable for my inappropriate action.
Please accept my deepest apology for my insulting behavior toward you. This letter is not sufficient enough to explain my feelings of embarrassment but I want to let you know that it all happened unintentionally. I was under a state of mental pressure and stress due to continuous and unstoppable work in the office.
I was arrogant and disrespectful that day but honestly speaking, I have never anticipated it to happen in front of you. You are my immediate boss and this is my moral as well as first and foremost duty to respect you. Despite my arrogance, I still believe that you are a kind-hearted person and have a soft corner in your heart to accept my sincerest apology and forgive me. I am waiting for your response. Once again, I am sorry.

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