This is the part that always tears me in half:

"I will tell you truths while I can, satisfied with proving myself your friend by very faithful counsel, and trusting that you will some time or other do me greater justice than you can do now."

This chapter is always hard for me to read, but I think it shows Mr. Knightley at his best: he defends Miss Bates, urges Emma toward more careful consideration of how to use her influence for the best, and provides one of the best literary examples ever for the Bible verse, "faithful are the wounds of a friend." I believe Austen also shows how sensible and realistic he is by his comments on how things might be different if Miss Bates were richer and more powerful; Emma's remark would be thoughtless and insensitive in any circumstances, but he knows when a rebuke is really appropriate. This isn't one that she can shrug off the way she does with some of the rest---no lighthearted handwave about him being her severest critic here.