Yeah William Henry Harrison had a pretty crap 100 days since he was dead for most of them.Ooooh. I'm struggling to think of any president in recent times that comes close. The bloke who caught a flu and died?
cc @Carolina Red
The only "first 100 days" I can think of that come close (other than Harrison dying) are Lincoln, who had states declaring secession, and JFK, who had the Bay of Pigs.