Well, I think it's clear that the worst team in the league is the Colts. The Dolphins have been reasonably close in a couple of games.
Indy has:
lost by 27, 8, 3, 7 , 4 , 10 , 55
Miami has:
lost by 14, 10, 1, 10, 18, 3
Two one score losses by Miami and four one score loses by the Colts. Both have been in games late and come up short, I'm not sure who's worse myself.