James T. Kirk (mirror)

In the mirror universe, James Tiberius Kirk was a Starfleet captain, but rather than the Federation "our" universe's Kirk worked for, he was loyal to the brutal Empire.

Kirk succeeded to command the ISS Enterprise through assassination of Christopher Pike. His first action was the suppression of the Gorlan uprising through destruction of rebel home planet. His second action was the execution of 5,000 colonists on Vega IX. Kirk's rise to power was very much due to his possession of the Tantalus field, a device he stole from an alien scientist, that allowed Kirk to vaporize uncooperative enemies remotely, without evidence. However, Kirk also had a personal security squad as bodyguards, led by Mr. Farrell. His woman in the late 2260s was Marlena Moreau, a lieutenant assigned to the sciences division (and also a skilled assassin).

In 2267 he visited the home planet of the Halkans. The Empire had noted their homeworld's vast dilithium reserves and threatened to destroy them if they did not comply. When Kirk's landing party attempted to beam up from the Halkan homeworld, an ion storm crossed him with his parallel from this universe, beaming him right inside his duplicate's clothes in a one-in-a-million transference, which read to Kyle's board as a "wobble" in the power beam of the transporter.

He found himself aboard the USS Enterprise in a different world than he knew – Spock noted it was more difficult for the barbaric mirror landing party to behave civilized than it was for the civilized crew to feign barbarity on the other side. After being imprisoned by Spock, he offered him fantastic bribes to get his command back. Spock proceeded to place the captives on the transporter, to wait for when the crew from his landing party reciprocated the action, and beamed themselves back into the places of the duplicates. 

It was later revealed by Intendant Kira to her counterpart Kira Nerys, during a second crossover into the mirror universe in 2370, that Kirk's situation upon his return would be far different. His Spock had relieved him of command, and had Kirk's Tantalus secret and the loyalty of his woman. Kirk's duplicate had strongly encouraged them to attempt to overthrow and change the Empire's negative effects on the galaxy.

Upon relaying this information to Julian Bashir, he noted that the events leading to Kirk's overthrow was something he read at Starfleet Academy.