IG-88 was an assassin droid-turned-bounty hunter. He and several others were summoned by Darth Vader to the Executor after the Battle of Hoth, and ordered to fulfill the bounty on Han Solo. However, it was Boba Fett who tracked down Solo in the Millennium Falcon. After Han Solo was captured IG-88 was given another assignment. In the next assignment he was instructed by Darth Vader to Capture or Kill Dash Rendar. Even though he was tasked with Killing Dash Rendar he still had plans to confront Boba Fett later on and take back Han Solo from Boba Fett. Acording to George Lucas as seen in the Movie Star Wars Return of the Jedi its clearly shown that IG-88 failed in this task of Getting back Han Solo from Boba Fett as you can see that, Han Solo had been delivered to Jabba the Hut.
Although, it's not considered official canon by the Star Wars community. According to LucasArts, the ultimate fate of IG-88 was that he was to be killed by Dash Rendar on the junk yard planet. It remains unclear what the canonical fate of IG-88 was according to George Lucas. Its possible that in George Lucas's version IG-88 was killed by Boba Fett instead becasue Dash Rendar never exsited in the original Script for any of the original star wars movies. This movie theory of "IG-88 was supposed to be killed by Boba Fett" makes sense coincidering that in the game IG-88 had plans to confront Boba Fett over Han Solo anyways. Theoretically speaking if the game player dies during the IG-88 duel or boss battle history will resume its regular course and every thing remains canonical acording to the George Lucas version of the events around the character IG-88.