This is interesting because you can take the trade in isolation, and at the time it was made -- or you can extrapolate, either based on what players have become, or what assets have been turned into, or both.
I have a weird feeling that Jake falls into that Brassard category of becoming more somewhere else than he would have here. I loved the kid, thought he'd be really good, but he was part of that generation here, and had some things to say about the org and town if I recall after he left. And Jagr was credited for getting him to take the next step. Still, that's gotta be the worst.
Except for maybe March 9, 2004, when the Jackets acquired Brian Holzinger from the Pens for... Lasse Pirjeta.
In terms of what players became, Glencross-for-Tarnstrom has to be one of the worst. Taken in isolation, it was a good trade IMO.
The saddest was trading Klesla to Arizona for Lepisto and Upshall, even though I liked both of those players.
If you're going to extrapolate future play, Mason for Leighton and a 3rd is bad. At the time, it was totally defensible.
In terms of asset management, the trade away of Gaborik to the Kings hurts bad.
My daughter's favorite player was at one time Kris Russell. We got her a jersey with his name and number for her birthday - late October 2011. Like two weeks later, he was traded.