1The company's CEO was accused of acting treacherously towards the shareholders by concealing the true extent of the financial crisis.
2The treacherously steep slope made it difficult for the hikers to climb down without risking a serious fall.
3The novel's protagonist was shocked to discover that her best friend had been acting treacherously behind her back, spreading rumors and lies about her.
4The treacherously calm surface of the lake belied the strong currents that lay beneath, posing a significant threat to swimmers.
5The historian argued that the government's decision to go to war was a treacherously flawed one, based on incomplete and misleading intelligence.