When Doctor Who debuted way back in 1963, neither the BBC nor audiences knew what to expect. In order to capture the imaginations and hearts of would-be fans, they would need a colorful and entertaining list of monsters and villains for the titular Doctor and his companions to battle.
Some were ambitious humans, others were paranoid aliens, and one particular foe would go on to become the Doctor's most infamous foe. However, all fans will agree that all these villains have proven to be memorable in their own right.
Léon
It's hard to classify Léon as a full-scale villain, given the fact that he was acting in the best interests of his own ideology. He was a revolutionary from the 18th century who appeared in the serial "The Reign of Terror," which probably took a few cues from several Hollywood films based on the historical French Revolution.
At first, Colbert appeared to be charming and benevolent, but he betrayed them after setting a trap for Barbara and Susan, and then Ian shortly thereafter. In truth, he was a double-agent who tried to infiltrate the counter-revolutionary group. He ended up dying during a raid by Jules Renan to rescue Ian.
The Doctor
The third serial "The Edge of Destruction" was created as a fallback in case the show's ratings declined, and the bulk of it took place within the Tardis. The story itself was an interesting one that revolved around the Doctor and his companions suffering from a strange form of rampant paranoia and suspicion.
Throughout this ordeal, it is the Doctor who reveals himself to be the true villain. His worst traits bubble to the surface, including malice, which has a profound impact on his companions. Eventually, it is learned that the Tardis itself was trying to communicate an impending catastrophe to the crew, at which point a lucid Doctor is forced to apologize in humility to Susan Foreman, who he was particularly hard on.
Tegana
Unfortunately, the serial "Marco Polo" has been completely lost to time, thanks to oversight by the BBC during the early days of production. As such, it's hard to fully gauge Tegana's presence as a villain, as only the audio recording remains in existence.
Tegana was an assassin, posing as a peace emissary, who sought to kill Kublai Khan in 1289. His suspicion of the Doctor and his companions prompted him to try and eliminate them from the onset, but they were stopped by Marco Polo himself. At one point, he even attempted to steal the Tardis, but his machinations finally came to a halt when he chose to take his own life after being defeated in a duel with Polo.
Kal
Kal was the first true villain of Doctor Who, introduced in the series' debut episode "An Unearthly Child." After the Doctor and his Tardis were discovered in a junkyard by Coal Hill high school teachers Ian Chesterton and Susan Foreman, it forced the Doctor to whisk them back in time to an age where humans are still struggling to make fire. It is here that they encounter the ambitious and villainous Kal, who is from another tribe.
Kal's popularity grows as he brings meat back to his new tribe, while their leader Za still struggles to master the art of fire. He attempts to force the Doctor and his companions to show him the secret of fire, sparking an intense rivalry that nearly leads to their deaths. In the end, Kal's villainy leads to his own death at the hands of Za.
Vasor
This villain was introduced in the serial "The Keys of Marinus," and he proved to be one of the most ruthless and unscrupulous of the bunch. A trapper by trade, Vasor rescues Barbara and Ian from death in a freezing wasteland, but it soon becomes clear that he's no hero.
He attempted to kill Barbara before being stopped by Ian and his friend Altos, at which point he feigned fear in an attempt to save his own skin. Later, he'd betray them again inside an ice cave before finally meeting his end at the hands of a mechanical Ice Soldier.
The City
Season one introduced audiences to the Sensorites, a race of bipedal humanoids with extraordinary telepathic abilities. It was an intriguing and thought-provoking story that also gave the First Doctor one of his best quotes of his entire run. The first few episodes painted them as villains, but it was later learned that they were actually a benevolent and largely peaceful race ruled by fear of humans.
The Doctor managed to gain the trust of the First Elder, but the City saw him and his human companions as dangerous usurpers out to eliminate the Sensorite race. Driven by a lust for power, this cunning and conniving elite defied every Sensorite cultural norm in an attempt to destroy what he perceived as a threat.
Kala
A surprise villain of season one was Kala, a young woman who feigned innocence and sweetness in order to cover up her participation in a plot to steal one of the keys to the Conscience of Marinus. She was part of a triumvirate that went to great lengths to weave a web of deception in order to hide their tracks.
Kala was the most unscrupulous of the bunch, killing one of her own co-conspirators just to silence him, while kidnapping Susan and threatening her life. She slipped up when she revealed information to Barbara that allowed her to deduce who the real conspirator was. Kala and her remaining co-conspirator Eyesen confessed to their crimes.
The Daleks
The Doctor had never even heard of the Daleks before his ill-fated visit to Skaro along with Barbara, Ian, and Susan. There, they discovered a planet ravaged by war and nuclear holocaust that left only the surviving humanoid Thals and the mechanically encased Daleks standing.
Not only did their first appearance in Doctor Who set off a pop culture firestorm, but it also solidified just how evil and unfeeling the Daleks truly were. Genocide was a norm for them, as was cruelty, malice, and selfishness. While relatively tame compared to future appearances, the Daleks established themselves as the premier villains of season one, not to mention the entire series.