Wesley Crusher

Wesley Crusher was a antagonist found in several off shoots of the mirror universe.

Dark Mirror
In the Dark Mirror universe where the Terran Empire and its Imperial Starfleet had survived in to the 24th century, Crusher was an ensign on board the ISS Enterprise (ICC-1701-D), under the command of Captain Jean-Luc Picard.

Crusher loathed Picard for murdering his father in order to have Crusher's wife Beverly as his Captain's Woman. This loathing led Crusher to make an attempt on the prime universe Picard's life while that Picard was posing as his mirror universe counterpart. First officer Riker was aware that Crusher would make an attempt, and was hoping that Crusher would succeed so that he could take command of the Enterprise.

Picard's personal guards placed Crusher in an agony booth for his attempted assassination of Picard. The prime universe Picard ordered Crusher removed from the booth and confined to quarters.

Mirror Broken
In the Mirror Broken off-shoot of the mirror universe, Crusher was brought on board the ISS Enterprise (NCC-1701-D) by his mother. He helped run the agony booth to torture disobedient crew members, and at one point got to torture Picard in the booth. He was later named as a conn officer on the Enterprise after the two strongest candidates for the position were killed when Picard took over the Enterprise.