Who is the Doctor's arch-nemesis?

The Doctor's arch-nemesis is the Master, a Time Lord who was once the Doctor's childhood friend on the planet Gallifrey. Throughout the Doctor Who franchise, the Master has been portrayed by various actors and actresses, each bringing their own unique interpretation to the role. The Master is a recurring villain in the series, and has clashed with the Doctor numerous times throughout their respective regenerations.

As a Time Lord, the Master possesses many of the same abilities as the Doctor, including the power to regenerate and the ability to time travel. However, the Master has often used these abilities for nefarious purposes, such as attempting to conquer the universe or destroy the Doctor and their companions.

The Master's significance to the Doctor Who franchise is not only due to their role as the Doctor's nemesis, but also due to their complex relationship. The two Time Lords have been shown to have a deep bond that goes beyond their rivalry, with the Master sometimes assisting the Doctor in their battles against other foes. Additionally, the Master has also had several redemptive storylines throughout the franchise, such as the character's portrayal in the most recent series, where the character regenerated into a female form and became a hero in her own right.

The Doctor's arch-nemesis is The Master. He is a Time Lord, a renegade like the Doctor himself, but one who has embraced the dark side of his nature. He is a brilliant scientist and a gifted manipulator, and he is always scheming to take over the universe. The Doctor and The Master have been enemies for centuries, and their rivalry has been one of the most enduring and popular aspects of the show.

The Master has been played by a number of different actors over the years, including Roger Delgado, Peter Pratt, Anthony Ainley, Eric Roberts, Derek Jacobi, and Michelle Gomez. Each actor has brought their own unique interpretation to the role, but they have all captured The Master's essential qualities: his intelligence, his ruthlessness, and his undeniable charisma.

The Master is a complex and fascinating character, and he is one of the reasons why Doctor Who has been so popular for so long. He is a villain who is both terrifying and compelling, and he always makes for an exciting and unpredictable story.