After all the trouble that he caused to the other European countries why did they decide to exile him to Elba instead of directly killing him? They'd have avoided the 100 days goverment
Take a look at this excellent answer from /u/kieslowskifan.
https://www.reddit.com/r/AskHistorians/comments/3r6qy0/why_was_napoleon_exiled_rather_than_executed/cwlv0f8/?context=3