Ha! Beat him with Wrinkle from Mage the Ascension (one of the the most powerful Paradox spirits. Also a Paradox spirit of Time). His first guess was Q from Star Trek, then The man from another place from Twin Peaks and finally the wizard of Oz.
Well, but I'll cut him some slack, Wrinkle hasn't really been around since second edition, so he might be a bit obscure.
I tried Voormas next. Still Mage the Ascension but this guy is more popular. Pretty much the poster child of don't let death magic go to your head. Akinato didn't manage to guess him. But at least this time asked if that was a character from a tabletop game. Well, it was five questions from the end but still better.
EDIT: Totally ruined Akinator with Azathot. Well, Akinator kept asking be about physical characteristics (Is your character blond?) and other that could in no way be related to it (Does your character wear pants?). The guesses were "Nobody", "A character I cannot guess because it doesn't exist" and "Your plant".
In all fairness, Azathot was there at the very end when it asked me if it's any of these characters. A step above from the Mage ones.