Ira Gaines: leader of mercenary group hired by the Drazens, whose group was tasked with killing Palmer and making Jack the scapegoat; shot by Jack when he infiltrated the compound
Rick Allen and Dan Mounts: helped Gaines kidnap Janet York and Kim Bauer; Dan was killed early on, but Rick later escaped with the Bauers and was later arrested with Kim during a drug raid
Ray Mercer: mercenary working for Gaines who was recognized and incriminated under the name "Jenson" by Teri via his mugshot
Joe: a mercenary working for Gaines at his compound, who helped load up the vans
Mandy: expert assassin; she was given one million dollars for blowing up Flight 221 from Germany, to get a hold of Martin Belkin's ID card; had partner Bridgit retrieve it afterward; disappeared after her part was done
Bridgit: Mandy's partner, retrieved the ID card of Martin Belkin for an extra million dollars; killed by Jonathan for her extortion after giving up the card
Jeep driver: escorted Mandy from the desert to Gaines' compound
Jonathan Matijevich: professional sniper who was surgically altered to look exactly like Martin Belkin and to assassinate Senator Palmer; fled the scene after failure
Jamey Farrell: mole in CTU turned by Ira Gaines; died of an apparent suicide after her discovery but was eventually found to have been murdered by Nina Myers
Drazen syndicate[]
Andre Drazen and Victor Drazen: masterminds of the day and leaders of the Drazen syndicate; Andre took his revenge plot in his own hands after Gaines failure, his role as the leader of the syndicate was overtaken by Victor after he was freed; both were killed by Jack after he thought they killed Kim
Alexis Drazen: expert sniper and assassin; Andre's brother, Victor's son; was stabbed by Elizabeth Nash and died just as he had been returned to his father and brother
Alan Morgan: electrician in Saugus paid off by Alexis to cut off the power at Grid 26-GG. Killed by Teddy Hanlin when he tried to escape
Jovan Myovic: assassin hired by Andre to kill Teri and Kim; attacked the safe-house and was later shot by Tony Almeida
Ted Cofell: financial backer of the cell; kidnapped and interrogated by Jack, through his info did Jack establish the Belgrade connection; died after refusing heart medication after being punched in the heart
Nina Myers: highly-placed mole working for the Drazens through an unknown German party; murdered Jamey Farrell and Teri Bauer and tried to escape CTU; arrested and sent to prison upon discovery
Marko: Serbian terrorist hired by Andre; killed by Jack at the pier
Boris: Serbian terrorist hired by Andre; transported Jack from the restaurant to the oil pumps
Serge: Serb working for the Drazens who gathered Alexis from George Mason then returned to the pier; searched for Kim when she escaped; apparently killed by Jack at the pier
Harris: Serbian exile and leader of a military guerilla force working for Andre Drazen; broke into the Class 3 Detention Facility in Saugus to rescue Victor
Nikola Luminović: an old friend of Victor who sheltered him after his escape, but was murdered by Victor nevertheless
An unidentified mole within the United States intelligence community, who used the codename Dagger, responsible for leaking details of Victor Drazen's imprisonment to Alexis for one million dollars (Findings at CTU)
Lucy: prisoner who attempted to frame Melanie for smoking pot
Miscellaneous[]
Teddy Hanlin: sniper with animosity towards Jack who jeopardized the investigation by, against Jack's direct orders, shooting and killing a suspect
German contact: unidentified woman represented Nina Myers's German employer(s), and was contacted by Nina in the last hour of the day to assist in her escape
Ralph Rosen: was suspected of working for Gaines, but was not recognized by Teri or Kim