Most despicable? Doukoku!!! HE DIDN'T GIVE US MUCH ACTION!!! ALL HE DID WAS SIT THERE, WHINE, AND DRANK HIS SAKE!!! Now that's despicable...
He couldn't enter the human world at his own will at the time because he would dry up faster, as seen in episode 40, which is why Shitari had to drag him back to the Sanzu River just so that he could be rehydrated. Plus he was too overpowered, as seen in episode 40 & in the last two episodes of Shinkenger. That seemed like a good reason to not have him do anything until those three episodes.