As a character, or you as a person?
The evilest thing I could picture him doing is giving someone a gag gift for Christmas as a prank, and even then I'm sure he would feel very badly about it afterwards.
Having no knowledge of the fellow, I won't vote on it.
Out of vague curiosity... why are you asking this? Is this something you might want to expand on?
Also, if you're feeling like Nautilus is a rotten human being, it's worth mentioning that opening an impressive underwater University for anyone, from the descendants of imperials to the scum of Aethasia, to live in for free no strings attached is by far the kindest, most selfless thing anyone could possibly do in a role play.
If you want to feel less awful about yourself, read my role play Ever-glowing Embers: Story of the Emberlins or A Series of Unexpected Escapades and I assure you, you'll feel like a saint.