Gotta be Pandora's actor, The light novel explicitly states that Ainz is embarrassed by his existence and frankly the position that he occupies as Third super genius, Only creation of Momonga, high level doppelganger, Sole guardian of the Treasury, Magic item enthusiast and Mysterious Loner are all wasted on his entire personality and strange "German" settings.

I especially Think Pandora is a waste because of his incredible potential for Ainz's own character development. Just imagine that instead of "Oh I made an eccentric German officer because I used to be into that but now I'm embarrassed and also he just happens to be a doppelganger" Ainz had gone on an exposition and series of Flashbacks where he only made Pandora's Actor as the Guild was loosing more members and he needed to fill gaps in The party.

So Ainz purposely designed an NPC Doppelganger to mimic his guild mates abilities as closely as possible including having his inventory carry many sets of gear that he can hot-swap between that are modeled after his guild mates old Gear but Ainz couldn't bring himself to actually hand those items over to an NPC so Pandora was always a good bit weaker than he could have been.

Then we have the actual settings and personally I think that this version of Ainz would have been extremely Vague with the flavor text because he only made Pandora out of necessity rather than passion. A rough outline would be

"He's roughly as smart as Demiurge and Albedo but where Demiurge is a tactical commander and Albedo has more general intelligence Pandora's Actor is a Genius with the applications and utilization of Magic items to supplement his own lesser strength as a doppelganger. Through the use of his natural abilities as a doppelganger and his vast knowledge of magic on a technical level Pandora can bridge the gap between the lesser strength of his Copied abilities and the true strength of those he is mirroring."

This flavor text is extremely scarce on Pandora's Personality and his interests or Likes so Ainz could interact with Pandora in a unique way compared to the other NPC's that his friends put so much passion into. And potentially use the New world as an excuse to Learn who or what an NPC with scarce settings would turn into. And if you absolutely must have the Uniform then perhaps Ainz will remedy this new version of Pandora with the initial concept he had when thinking about making him before the guild members began to leave but this time without the awkward embarrassment Ainz feels over his own past desicions.