What expression fits best when referring to someone who feels superior?

The best expression for referring to someone who feels superior is about looking down on others, which is aptly captured in the first choice. The phrase "look down your nose" implies a sense of disdain or condescension towards others, suggesting that the person considers themselves better, more important, or more worthy than those around them. This is a direct commentary on the attitudes of superiority, highlighting how someone might perceive others as lesser beings.

The other choices, while thoughtful in their own contexts, do not strongly convey the idea of superiority. Looking up to others suggests admiration or respect rather than a sense of feeling superior. Comparing oneself to others can denote introspection or competition, which doesn't directly imply a feeling of superiority. Acting better than others does relate to superiority, but it is less idiomatic than the phrase about looking down one's nose, which vividly captures the essence of arrogance and condescension that characterizes a superior attitude.