Antonyms for "placing trust in" can include doubting, distrusting, suspecting, questioning, disputing, and challenging. When we doubt, we lack confidence in someone or something's abilities or intentions. Distrusting implies a lack of faith or belief in what is being said or done. To suspect is to have a feeling that someone or something may not be trustworthy. To question is to express doubts or reservations about someone or something. To dispute is to challenge the validity or accuracy of something. Lastly, to challenge is to call into question and show a lack of faith in someone or something. In summary, these antonyms suggest disbelief or skepticism in relationships, actions, or beliefs that are typically accompanied by trust.