Which belief in particular made others Romans suspicious of Christians?

One belief that made Romans particularly suspicious of Christians was their refusal to worship the Roman gods and participate in traditional religious practices, including the veneration of the emperor. This perceived rejection of the established religious order was seen as a threat to social cohesion and stability in the empire. Additionally, Christians' exclusive allegiance to their faith and their belief in a singular God fueled suspicions of subversive behavior and disloyalty to Rome.