Sweeney was one of the most dangerous and legendary bounty hunters in the galaxy.
Sweeney was a bounty hunter that was greatly feared by the Federation, the Nasgul, and the Klingon Empire in the latter half of the 23rd century. In that time Sweeney commanded a group of six warships. Even Sweeney's own crew feared him. Sweeney wore special glasses capable of firing a laser at any target.
In 2287, following his capture and killing of Nanoc at the behest of Zagtun Bonecrusher, Sweeney was hired by both the Nasgul and the Klingon Empire to capture Starfleet Captain James T. Kirk. Sweeney went to Tau Gamma II to personally apprehend Captain Kirk, despite violating Federation law. As his warships attacked the USS Enterprise-A, Sweeney landed and introduced himself to Kirk, Spock, and R.J. Blaise. Sweeney announced his capture of Captain Kirk to the Federation and destroyed Kirk's phaser with laser goggles. Sweeney was able to defeat Kirk and Spock with his own hands and took Blaise, along with Kirk and Spock, up to his ship.
Sweeney placed Kirk and Blaise in his ship's brig while he hung Spock upside down, ignoring their pleas to help Tau Gamma II's colonists. Sweeney decided to play chess with Spock, knowing that Spock was not afraid of him. (TOS - The Trial of James T. Kirk comics: "Not... Sweeney!", "Going, Going...", "... Gone!")