I know midhawk isn't top tier but from the title I would have said that would be the biggest bum, not Shanks.
We have someone who runs away from the navy and teams up with Luffy's rookie victims vs a guy who makes the navy, midhawk and blackbeard run away multiple times. He might not have wanted to challenge Whitebeard or Kaido in the race to becoming pirate king, but he certainly took them on without hesitation when they were standing in front of him. The same cannot be said of Mid.