Top Five Villians of 24

1. Nina Myers (Days 1, 2, 3)
The quintessential villian of the series, Nina was Jack's co-worker at CTU and his former mistress. It turned out that Nina was a traitor, working undercover to effectuate the assassination of Senator David Palmer. Once her plan was foiled, she made arrangements to escape, but only before killing Jack's wife, Teri. In later seasons, she sold plans of CTU to a terrorist group that bombed it and released a computer virus into CTU's system that compromised its information to terrorist cells around the globe. Nina was about to kill Jack's daughter, Kim, before she was gunned down by Jack himself.

2. Christopher Henderson (Day 5)
A former member of CTU who was fired for taking bribes, Henderson developed a vendetta against Jack for blowing the whistle on him. Henderson became an executive of a defense contractor, using his position to supply Russian terrorists with nerve gas. In an attempt to save himself and pursue his vendetta, he attempted to kill Jack by blowing up a warehouse, allowed Jack to cripple his wife with a point-blank gunshot, survived a medical interrogation intended to kill him, stabbed former CTU director Tony Almeida with a lethal syringe, and after weaseling his way out of CTU custody, attempted to shoot Jack, only to find that his gon wasn't loaded. Jack took the opportunity to kill Henderson once and for all.

3. President Charles Logan (Days 4, 5)
Initially appearing as an indecisive and incompetent leader of the country, President Logan turned out to be a key player in a conspiracy that would allow Russian separatists to steal Sentox nerve gas and use it to foment revolution, that would ultimately lead to cheap oil for the United States. Logan even allowed a motorcade carrying his own wife and the Russian president to steer straight into a terrorist ambush. Once things went wrong, Logan did whatever it took to cover his own tracks, including authorizing the military to shoot down a commercial flight carrying fifty-plus diplomatic passengers.

4. Habib Marwan (Day 4)
This mastermind infiltrated a defense contractor and used its technology to have his sleeper cells carry out a litany of terrorist attacks during the course of the day. Marwan arranged for the bombing of a commuter train, the kidnapping and attempted execution of Secretary of Defense James Heller, the meltdown of several nuclear power plants, the destruction of Air Force One and the permanent incapacitation of President James Keeler, the theft of the nuclear football and a nuclear warhead, and a nuclear strike on Los Angeles that was thwarted at the last minute. Marwan committed suicide to avoid capture by CTU.

5. Navi and Dina Araz (Day 4)
As the terrorists next door, the Araz family was working for Habib Marwan as part of a plot that would ultimately launch a nuclear airstrike on Los Angeles. Navi ordered their son, Behrooz, to deliver a briefcase to a co-conspirator, but when Behrooz's American girlfriend shows up, she potentially compromises the mission. Navi and Dina insisted that Behrooz kill her, and when he refused, Dina did the dirty work herself. Once Navi realized that Behrooz is not on board with their cause, he sent a hitman to kill his own son. Because things are different when it is your child who is about to be assassinated, rather than someone else's, Dina helped Behrooz escape and Behrooz ended up killing Navi.