Why wasn't Napoleon executed?

Here's an interesting discussion about this question.

http://historum.com/european-history/18378-why-wasn-t-napoleon-executed.html

Napoleon Bonaparte, the French military and political leader, was not executed because he was able to escape from exile on the island of Elba, where he was initially sent in 1814 after the coalition of European nations defeated him in the Napoleonic Wars. After his return to France and the brief period known as the Hundred Days, he faced another coalition led by the Duke of Wellington and was ultimately defeated at the Battle of Waterloo in 1815.

Instead of executing Napoleon, the victorious coalition agreed to exile him once again, this time to the island of Saint Helena in the South Atlantic. The decision to exile Napoleon rather than executing him can be attributed to several factors. Firstly, his exile was seen as a way to prevent him from further destabilizing European politics, as executing him might have turned him into a martyr and potentially sparked more unrest. Secondly, his captors, particularly the British, did not want to act too harshly towards him, as they hoped to maintain good diplomatic relations with France in the post-Napoleonic era.

Ultimately, Napoleon spent the remaining years of his life in exile on Saint Helena until his death in 1821.