The phrase "turns traitor" refers to someone who betrays their country or cause. There are many synonyms for this term that can be used depending on the context, such as "deserter," "defector," "renegade," "turncoat," "double-crosser," and "Judas." Each of these words carries a slightly different implication, with "deserter" suggesting someone who abandons their post, while "turncoat" implies someone who switches sides. "Renegade" suggests a more rebellious or independent figure, while "Judas" has heavy religious connotations related to betrayal. Regardless of the specific word used, all refer to a betrayal of trust and loyalty.