Is it Batman? Spiderman? Superman?
Any Devil avatar or analogy in their respective universe, Gods of evil/mischief/treachery any of the sorts, and if you want to get omissions included, Superman mainly but also a bunch of other heroes are excellent liars by omission, hiding their identities very well
Also, if you want to get technical.
Mephisto can literally grow as big as an entire dimension!!! 0_o;
Making him literally the biggest liar in comics.
Loki can only grow as big as a one of the tallest buildings on Earth and that's just about it.