Who was the most overrated player in NFL history? Most underrated?

underrated - Gary Collins (wr/p) Cleveland Browns -- should be in the HOF, but he may still be in the doghouse with older sportswriters who vote / he demanded a trade from the Browns due to a new coaching regime or he said he would retire...team didn't deal him and he walked away from the game in an era when such individuality was only seen in Namath......overrated - Leaf, 'nuff said.