Firstly, I didn't want to make this a poll as I really don't think its good, there are too many characters, plus I want to hear why you think he/she is the most ruined person.
Also, by 'broken' I mean the most destroyed mentally, the most corrupted by the loss of society, family or just life as it was.
Personally I think Kenny is the most ruined, he has lost his family, the one thing he values above all else, to him the boat symbolizes his wife and child. And he'll do anything to get it, even if in the end it wont really make him happy. It just makes him less violent. Who do you guys reckon is the most crazy? Remember less major characters like the St. Johns, Joleene and the bandits are all totally acceptable.