The term DECEITFUL ONE can be summarized by three crossword solutions: SANDBAGGER (10 letters), CHEAT (5 letters), and LIAR (4 letters). A sandbagger is someone who deliberately understates their abilities in order to gain an advantage, while a CHEAT is someone who acts dishonestly or unfairly in order to gain an advantage. A LIAR is someone who tells falsehoods or untruths. All three of these terms describe someone who is deceitful and untrustworthy.