Not really sure what the build would be but have a guy that was his own (and his parties) worst enemy.

He has so much anxiety about failure that he somehow manages to snatch defeat from the jaws of victory.

Starting a fire on a wood boat.
Sneezing at just the wrong time.
Etc

It would be fun but at the same time a challenging balancing act so as not to do something that will kill the party, just make everything harder than it needs to be.