The term 'untrustworthy one' can be used to describe someone who is deceitful, dishonest, and untrustworthy. This can be seen in the crossword solutions for the term, which include KNAVE, SNEAK, JUDAS, SERPENT, CHEAT, SCAMP, LIAR, ROGUE, RAT, SNITCH, and RASCAL. Each of these words has a negative connotation, suggesting that the person being described is not to be trusted. Additionally, some of the words, such as JUDAS and SERPENT, have religious or mythological connotations, further emphasizing the idea of untrustworthiness.