Final answer:
Chillingworth's physical appearance, actions, and association with dark elements reinforce the image of him as someone to be feared.
Step-by-step explanation:
The details that reinforce the image of Chillingworth as someone to be feared are his physical appearance, his actions, and his association with dark and mysterious elements. Hawthorne describes Chillingworth as having a "ghastly look" with "profound, and wary, even though unwarlike, intelligence". This description and his physical deformity contribute to his menacing presence.
Furthermore, Chillingworth's relentless pursuit of revenge against Dimmesdale and his malicious actions, such as psychologically tormenting Dimmesdale and using his knowledge to control him, solidify his reputation as someone to be feared.