1. Luol Deng
The worst free agent signing in Laker history is pretty easily Luol Deng, and his contract is arguably one of the worst in NBA history.
In the same summer that the Lakers locked up Mozgov to big money, they inexplicably did the same thing with an aging Luol Deng. They ended up signing Deng for an astounding $72 million for four years. That is the type of contract you give to an All-Star level player. Instead, the Lakers gave it to the diminishing Deng.
His contract was so bad that it proved to be immovable around the league and not a single team would entertain the Lakers in trade talks for him. They could not get rid of Deng until this offseason when they used the waive and stretch provision to buy out the final two years of his deal.
As a Laker Deng only played in 57 games in two seasons with the team and averaged just 7.6 points in those games. Saying his Laker career was a disappointment is the understatement of Lakers history.