look down nose
look down (one's) nose at (someone or something)
To regard oneself as superior to others and thus act in a haughty or snobbish manner. The well-dressed businessman looked down his nose at the homeless man sitting on the corner. Once Jane was promoted to management, she looked down her nose at the people who used to be her colleagues.
look down (one's) noseat/on
To regard with contempt or condescension.