Sorry about that = “Looks like I gave you the wrong phone number. Sorry about that.”
I am (so/very/really/terribly) sorry = “I lost the book you lent me. I’m so sorry!“
Oops / whoops = “Oops / whoops – I just spilled some coffee. I’ll clean it up.”
My bad = “Oh, I sent you the wrong link. My bad.”
I take full responsibility = “I take full responsibility for failing to train the employees properly.”
I messed up = “I can’t believe I forgot your birthday. I messed up.“
My apologies = “My apologies for keeping you waiting. I’m running a little late today.”
I owe you an apology = “I owe you an apology. I said some horrible things to you.”
I shouldn't have taken / I should have asked = “I shouldn’t have taken your camera. I should have asked you first.”
That was wrong of me = “I gave you the silent treatment, and that was wrong of me.”
I'm ashamed of my behavior = “I haven’t been helping you around the house at all. I’m ashamed of my behavior.”
I truly regret = “I truly regret my offensive comments.”
We sincerely apologize for the inconvenience = “Our website is not working properly. We sincerely apologize for the inconvenience.”
“I won’t do it again / It won’t happen again.”
How can I make it up to you = “I’m sorry I had to work late, and missed our date. How can I make it up to you?“
“Pardon?” Or more informally, “What?” or “I didn’t catch what you said.”