- You use at all when you want to emphasize that you are talking about any and every case.
- The school has done nothing at all to help us.
- Can you lend me any money at all?
- "Do you mind if I sit here?" "No, not at all."
- If anyone at all wanted to keep this, we would keep it.
- At all is mostly limited to negative contexts, questions, or conditional situations. Its use is limited in declaratives to the same cases where any can be used.
- Any person at all is welcome. (grammatical)
- *I have some bread at all. (ungrammatical)