As others have said, 'any harm' implies that there might be none, while 'all harm' implies there is definitely some harm. So, 'all harm' is definitely the bette

As others have said, 'any harm' implies that there might be none, while 'all harm' implies there is definitely some harm. So, 'all harm' is definitely the better choice of words for an apology (in this context.) I am surprised to see people hung up on this, because the rest of the letter acknowledges specific harms done. To me, it really seems like a minor thing, and something that I might have written (as a native English speaker.)