Outside of the Thornton trade (arguably, he qualifies due to playoff failures), there's always been a fly (if not a roach) in the ointment of the player being acquired. Burns had tremendous talent (basically freakish physical tools) but had struggled to put it together and was highly unlikely to re-sign in Minnesota. Heatley had a monstrous contract and a NTC. Boyle was not quite an elite talent, had disputes with TB management, was coming off of a long injury, and had a fat contract. Karlsson had the injury history and was also on an expiring contract.
Dubois and Eichel both have their squabbles with management, and Eichel has the fat contract...