In terms of results for money, Sandoval is far and away the worst. In terms of worst idea, CC's re-signing is up there.
Gonzalez was a pretty good idea - he looked every bit that player early ... and to be fair to him, he had about 5 years of the deal where he was at least a good MLB 1B. A disappointment relative to salary - but not a horrific one.
As much as anything Gonzalez trade, while a dump - was really also giving the Dodgers some actual quality to absorb Beckett and Crawford's deal.