colluder
/ˈkɒl.jʊdər/Definitions
1. noun
A person who colludes, especially a person involved in a conspiracy or secret agreement with others
“The politician was accused of being a colluder in a major bribery scandal.”
2. verb
To conspire or secretly work with others, especially to achieve a forbidden or illicit goal
“The two companies were accused of colluding to fix prices in the market.”