Here you are, closing those eyes, trying not to see what bitterness has done to the Son'a. How it's turned Ru'afo into a madman. And you? It's turned you into a coward.
~ Picard pricks Gallatin's conscience
Gallatin is the (former) secondary antagonist of the film Star Trek: Insurrection.
He was portrayed by Gregg Henry, who also portrayed Martin Proctor in Black Lightning and voiced Brother Blood in Teen Titans: The Judas Contract.
Gallatin was born Gal'na of the Ba'ku. Disagreeing with the Ba'ku's rejection of modern technology, Gal'na followed his friend Ro'tin in attempting a coup against the Ba'ku leadership. They failed and they and their followers were sent into exile. They became the Son'a, with Ro'tin becoming their leader Ahdar Ru'afo and Gal'na becoming his second-in-command Gallatin, with the title of subahdar.
Their new civilisation became so well-established that the galaxy at large was unaware of their origin. However, deprived of the metaphasic radiation that had kept them young, their bodies began to break down. They contacted the Federation, in whose space the Ba'ku homeworld was located, and convinced them to displace the Ba'ku and allow them to activate a collector that would harvest the radiation for medical use, including saving their own lives. They were assisted in the scheme by Starfleet Admiral Matthew Dougherty.
As cover for the plan to abduct the Ba'ku using a holoship, a joint Starfleet/Son'a team infiltrated the Ba'ku planet as cultural observers, with Gallatin leading the Son'a contingent. Data learned the true plan and exposed the observation team, leaving them with the Ba'ku. They were later collected without a struggle by Picard and the rest of the Enterprise crew. In order to hide their true nature, Gallatin and the other Son'a refused to submit to medical examination and were held in quarantine until Dougherty ordered them returned to Rua'fo.
When Picard and the Enterprise crew interfered in plans to beam the Ba'ku off the planet, Rua'fo wanted to send down an assault team and take them by force. Dougherty was reluctant to authorise violence so Gallatin suggested an alternative: Sending drones to individually tag them with transponders. This saw a number of Ba'ku abducted, plus Picard. By now, the Enterprise crew had learned the truth about the Son'a, which they revealed to Dougherty and the Ba'ku.
Rua'fo's response was to decide to activate the collector immediately, which would kill everyone on the planet. He killed Dougherty and ordered Gallatin to imprison Picard and Dougherty's staff in the rear of the ship where the radiation would kill them. Picard convinced Gallatin to turn against Rua'fo and he helped beam Rua'fo and the bridge crew to the holoship. While Picard beamed over to the collector to stop Rua'fo activating it, Gallatin and Worf were quickly subdued by the rest of the Son'a but freed when their ship was damaged by the Enterprise and they were forced to surrender.
Afterwards, Gallatin visited the Ba'ku homeworld again and was reunited with his mother.