Only one man can rise to the top in that category: Jimmy Carter. Carter's psalm-singing sanctimony would be annoying enough if he just confined his antics to housebuilding, instead he uses his position as an ex-president to preach against the war, belittle our current policies and stick his nose in where it doesn't belong by "certifying" elections that elevate the strongmen he so admires throughout the world. And because he's an ex-president, current presidents can't tell him to fuck off. And newspapers give him prominent space on their editorial pages.
(On a side note, the blogosphere is abuzz about the call from former Carterites to preemptively strike against the North Korean Taepodong missile. Of course, we mightn't be facing the North Korean threat if Jimmy Carter hadn't abused his position by flying off to North Korea to "help" the Clinton administration.)
Others who fit the definition (in no particular order):