There have been so many bad contracts in the NBA over the years it's impossible to list them all. Most of them came in the late 90's and early 2000's, part of which is why there were successive lockouts.
Recently, however, Chandler Parsons, Joakim Noah, Timofey Mozgov, Tristan Thompson, and Luol Deng all stand out as players who pretty much contributed nothing, but all received huge paydays.
A couple of the past players I remember, whom signed terrible contracts were Eddie Curry, Rashard Lewis, Juwan Howard, Vin Baker, and Eric Dampier, to name a few