Ultimate Commendation

Ultimate Commendations are an elder game commendation that can be earned from operation bosses and by completing level 55 weekly missions. They can be used to purchase specialty items from Ultimate commendation vendors. Ultimate Commendations have a max limit of 300 and a weekly earning limit of 150.

Source
Ultimate Commendations are mission rewards that can be obtained from hard mode operation bosses in Scum and Villainy and Terror from Beyond. They can also be obtained from weekly missions.
 * Mission reward