The last Warlock to stand on Mercury
On November 9th right before Destiny 2 was taken down for a 14 hour maintenance to integrate the massive Beyond Light update all players gathered to watch as the Traveler reformed itself and ushered in the new year of content to players.
The 4 destination: Mercury, Mars, Titan, and Io were going to be deleted as far as we know and never to be played on again. But in the brief period after the cutscene triggered that would start the maintenance players could skip the cutscene and load into one of the destinations in the game. With only around a minute to do so it's unlikely many people actually took notice and were able to load into a destination.
Thus it can be stated with a modicum of confidence that I in this video was the last player to stand on Mercury before it was deleted from the game.