PatronLeomon is the Super Ultimate form of TantibusLeomon, and was designed by Grandis to be of two things; to be a shout-out to The Saint of Killers from the comic book Preacher, and to finally avoid the Digimon Cliche of having anything with so much as the name Leomon die by the end of the series. Just when things look bleak for Tenebrae, the sole TantibusLeomon individual in the Digimon Classic universe, he spontaneously digivolves into his final form to demonstrate to the heroes just how foolish they are for dare even thinking that just because he is a Leomon species, that he'll die all that easily, or better yet, even die at all, since his true form, PatronLeomon, is designed to be completely immortal due to insane experiments composed on it's DigiCore to make it completely indestructible. PatronLeomon isn't used much, though, since it's attacking skills are rather lackluster by comparison to it's sheer invulnerability towards everything.
"Not enough gun."
Scheduled to appear around the same time as Tenebrae himself, PatronLeomon serves as a living Deus Ex Machina much in the same vein that DeusGreymon exists at the end of the series. In fact, an early name for PatronLeomon was indeed DeusLeomon. While some other Super Ultimates make cameo appearances in the comic earlier than PatronLeomon's appearance, PatronLeomon is the first Digimon in the comic to be outright stated as being Super Ultimate, who thus explains that the cameo Digimon from before were also Super Ultimate as well. After allowing his own minions to escape, PatronLeomon leaves and says perhaps even the heroes will have a chance to achieve the power that he himself has.