I don’t think Putin is going to leave Crimea. It’s too rich in Russian history and mythology.
However, the west needs to make it so painful that he won’t risk another adventure in NATO countries like Poland or the Baltics.
So far the west has projected weakness. That will only encourage Putin to play the same game in Latvia or wherever else it suits him. A shooting war with Russia in a NATO country is just one step from WW3. No thanks. Better to deal with the KGB thug now.
Odessa will be the next flashpoint.