Vin Kollis was an officer within the Imperial Army, specifically the commanding officer stationed on Nishr during the period of the Galactic Civil War.
During 2 BBY, Kollis held the rank of Major General, and was given command of the Imperial forces deployed on Nishr, acting in the dual roles of garrison commander and planetary governor. Considered a relatively lenient officer by the standards of the Empire, he felt there was no need to interfere with the low-technology Nish population, but some soldiers disobeyed his directives, which sparked considerable unrest.
Despite his efforts to discipline the offending soldiers, the abuse of the Nish people continued, resulting in an uprising against Imperial authority in 0 ABY. This rebellion was put down with extreme force, and Kollis, perhaps against his own judgement, ordered TIE/gt attack fighters to bomb the three main Nish cities as a form of punishment. These events would later be known as the Nishr Suppression.
As a direct consequence, the Alliance to Restore the Republic dispatched SpecForce units to Nishr, which triggered the Nishr Campaign. Even though the Nish remained largely inactive following the brutal Suppression, and Kollis possessed a significantly larger number of troops compared to the Alliance's small Nishr Taskforce, he began losing territorial control due to focused attacks on his mobile units, eventually retreating to fortified positions around his garrison base.
Kollis requested reinforcements to push back the Rebel forces, but his superiors did not consider Nishr to be strategically important, leading to a prolonged stalemate.
On two occasions, Kollis is referred to as "Governor-General", seemingly suggesting that this title represented a combination of the functions of Governor and the rank of General. However, in reality, the title of Governor-General traditionally signifies a governor whose authority is "general" over other governors within their territory, and does not necessarily imply military generalship.