He is most well-known for being the driving force behind the creation of the Death Star, as well as being on board during its destruction.
In some universes, he was married to Thalassa Tarkin, while more often having an affair with Natasi Daala. Both would try to destroy the Rebellion in his honour, although neither were aware of his eventual cloning by Atha Prime.
One of the earliest variants of Tarkin was the AquilaenGrand Mouffe Tarkin, a religious figure affiliated with the High Council of Aquilae. Perhaps ironically, this Tarkin had nothing to do with his home reality's version of the Death Star, Darth Vader, or even the Empire itself.