'Superiority Complex' is rarely used in English - in fact I've never heard it outside of medical journals. There are lots of adjective for someone who think's they are better than others, however.
佢覺得佢屙屎冇臭味 is one we say in English a lot.
Also:
Inflated sense of self; high opinion of one's self, to have tickets on one's self
佢覺得佢屙屎冇臭味 is one we say in English a lot.
Also:
Inflated sense of self; high opinion of one's self, to have tickets on one's self