Supercilious is always used negatively, suggesting disapproval of someone's behavior or attitude. His supercilious manner made him unpopular at the office.
Pro Tip 2/3
Social Superiority
Superciliousness implies a sense of social superiority, as if looking down on others. Her supercilious comments about the event revealed her elitism.
Pro Tip 3/3
Emotional Context
When used, it often evokes emotions of irritation or resentment in others. His supercilious disdain for our project was very demotivating.