Here are some I'm sorry quotes:

1. "Not admitting a mistake is a bigger mistake." - Robert Half
2. "Never ruin an apology with an excuse." - Benjamin Franklin
3. "I’m not very good at saying sorry, but I apologize."
4. "The best way to have the last word is to apologize."
5. "Be the hero of hearts; learn to say I’m sorry."
6. "Mistakes are always forgivable if one has the courage to admit them." ^{therandomvibez.com 1}
7. "I’m sorry for the pain I’ve caused you. I deeply regret my actions and I hope you can find it in your heart to forgive me. I take full responsibility for my actions. I’m sorry for the hurt I’ve caused, and I will do everything I can to make amends." ^{graciousquotes.com 2}