As for me, I voted Leino. I think it's the worst because everything about it was garbage from the start. By any metric, it was a bad contract.
6 year deal at 4.5 million at a time when the upper cap limit was 56! It was silly money, at a sillier term. It was clear that a new owner, Pegula, was throwing money around, even with no one worth throwing at.
Then add on that he had little to no track record at the time. He had only just had a 20 goal, 50 point season at like age 26. He was never a full-time NHL'er before that.
And then top it off with the fact that Buffalo brought him in to be a center, when he was clearly a winger. How often noes that work out? He was put in the best possible situation to fail. All the expectations and demands in the world put on the guy.
Then he crumbled spectacularly. 25 points in his 1st year in Buffalo, and that was as good as it would ever get. He was eventually bought out after complaining in the medial constantly, and putting in only 2 goals in 2 years.
On his way out the door, he called the organization "jail".