I am aware he is already under the category however I think it's about time he deserves a formality post. Anywho let's begin.
DISCLAIMER: This proposal is ONLY referring to The Master from the CLASSIC era of Doctor Who not the revival from 2005 onwards.
Who is he?
The Master is the arguable main antagonist in the original run of Doctor Who from 1963-1989/1996 and in that time he's proved himself to be one of The Doctor's most dangerous opponents as well as one of the most evil characters in the entire series. He is a renegade Time Lord and the ex-best friend to The Doctor and an on and off ally to The Rani, who takes great pride in his destructive and ambitious nature, starting off as an entity who commits acts of chaos and destruction for sport he eventually became far more desperate to prolong his life as he grew closer to death something which made him far more dangerous than before. By the end of the series he resorts to trying to steal The Doctor's remaining regenerations something which nearly kills and wipes him out of existence before he's eventually revived by the Time Lords.
While later incarnations have shown a more sympathetic and tragic element to the character, all of the versions from this era in the show remain consistently ruthless and the levels of which go and up and down between incarnations.
What's the work?
Doctor Who was a long running science fiction series on the BBC and is one of the most iconic British properties in history. Although aimed mainly as family entertainment the show had a reputation for having certain horrifying concepts especially to children. The revival series although unrelated to this particular version of this character also has this reputation albeit not as strongly.
Throughout his time in the series The Master has built up an immensely large body count, several on screen some of which are fairly graphic such as when he snapped Chang Lee's neck, used his tissue compression device on several innocent bystanders over the course of his earlier appearances as well as when he stole the bodies of both Consul Tremas and Bruce effectively killing them by removing their essence. He also wiped out half of reality by accident but showed no remorse for this and even tried to improvise a plan around it, brainwashed and hypnotised several of his opponents, corrupted the android Kamelion and tried to use him as means for his own personal gains, tried to steal The Doctor's body, was responsible for the death of The Fourth Doctor, took over a planet full of Cheetah people which led to him corrupting a young man named Midge into working for him so he could go back to earth where he proceeded to kidnap the boy's mother and kill his cat in front of Midge's very young sister only to order Midge to kill himself after he failed to kill The Doctor. On top of this he usurped the throne of Trakken, blackmailed The Rani into helping him by withholding her ingredients and medication and has gone to great lengths to gain immortality including attempted assassinations and the aforementioned bodysnatching.
To compare him in heinousness to other villains in the series the only comparable candidates with sufficient resources somewhat equivalent to his would be.
- The Rani a psychopathic mad scientist and fellow renegade time lord who is also under the PE category who has been responsible for enslaving multiple civilizations, performing unethical experiments on humans and similar species she views as lesser than herself under the logic that it's not different to how they eat meat, brainwashing humans into mindless grunts to do her bidding, creating mutated creatures such as giant rats which killed the lord president of Galifrey's cat and even the current incarnation of the president himself, tried to drain the knowledge from geniuses across history, mutating people into things such as trees and killing The Doctor's Sixth incarnation by shooting lethal doses of a radiation fatal to time lords at his TARDIS.
- Davros the creator of the Daleks who was responsible for numerous amounts of death and mayhem across the galaxy as well as creating the most destructive and iconic monsters in the show's history, he's also killed several people to duplicate them into his goons, attempted to achieve his goal of destroying Galifrey on a few occasions, mutated two humans into new Daleks and tried to kill The Doctor on multiple occasions.
- Daleks who have been responsible for large numbers of death, destruction, enslavement and wars.
Two very small ones; the first being that in a cancelled final appearance back in the 70s he was supposed to redeem himself and sacrifice his life to save The Doctor, considering everything he did after that story was scrapped however and how he never showed any hint of redemption in the classic series it doesn't really count.
The second being how he is slightly taken aback by a couple of The Rani's actions in Mark of the Rani, this isn't because he feels sympathy or empathy for the lives she's ruining however it's because her methods were vastly different from his own preferred way of dealing with his enemies (i.e tissue compression/killing).
Considering the sheer amount of atrocities he committed in small part thanks to his numerous appearances as well as how he tops the heinous standards for recurring villains in the series I'd say he's an easy yes.