Commander Shepard (Renegade)

Evil-doer
Full Name	Commander Shepard
Alias	The Butcher of Torfan (Possibly)
Origin	Mass Effect
Occupation	Human Spectre, Commander of the Normandy, member of the Systems Alliance, member of Cerberus (briefly)
Powers / Skills	Superb combat capability, mastery over multiple guns, strong leadership skills, possible biotics.
Hobby	Abusing and mistreating other people, punching reporters in the face, murdering unarmed civilians
Goals	Stop the Reapers (Possibly Succeeded), kill aliens, further humanity's agenda (Succeeded)
Crimes	No information
Type of Villain	Protagonist Villain / Successful Villain / Dark Messiah / Evil Vs. Evil / War Criminal

“	Why would I ever betray you Wrex? I've known you a long time. It's just you and me, taking on the galaxy together.	„
	~ Renegade Shepard lying to Urdnot Wrex's face upon being confronted with their sabotaging the Genophage cure.

Important Note: Due to the nature of the Mass Effect series, how exactly Commander Shepard is depends entirely on the player. This article assumes the version in question is a "pure" Renegade, not a "Renegon" (mostly Renegade but somewhat Paragon). 

Though Commander Shepard is the main protagonist of the Mass Effect trilogy, he/she does not necessarily have to be a heroic character, and the Renegade iteration of Shepard is an extremely cruel, brutal, and militant individual who operates in a much more ruthless and callous manner than that of the more heroic Paragon Shepard.

An example of a female Renegade Shepard

An alternate male Renegade Shepard

Backstory

Like Paragon Shepard, Renegade Shepard has one of three possible backstories, either being the son of spacers, an orphan and former gang member from Earth, or a colonist from Mindoir who was orphaned during an attack by Batarian Slavers.  Renegade Shepard also has one of three possible "reputations": a War Hero, the Sole Survivor of a Thresher Maw attack, or (perhaps most likely) a ruthless individual who is already notorious for using any means necessary to get the job done, also being known as "The Butcher of Torfan". 

Villainous Actions and Tendencies

Throughout the course of the Mass Effect Trilogy, Renegade Shepard consistently shows either contempt or indifference to everyone around them, often being needlessly rude, patronizing, and insulting, even to friends and allies.  Renegade Shepard tends to have little if any sympathy towards the plights of others, and prefers instead to order angsting allies to "get over it". 

Renegade Shepard also displays homicidal and bloodthirsty tendencies, as shown by their always opting for a more violent and brutal approach to solving problems (as opposed to Paragon Shepard who generally tries to look for a better way than wanton destruction) and seems to relish fighting in general.  Renegade Shepard has also persuaded allies to indulge in their own darker inclinations, Garrus Vakarian in Mass Effect 2 being perhaps the best example of this. 

Though Paragon Shepard often manages to find constructive solutions to problems, as well as never endangering innocents if at all possible, Renegade Shepard has little patience for such things and believes in doing "whatever is necessary" to get the job done, regardless of "collateral damage".  Notably Renegade Shepard is shown to take a liking to Cerberus in Mass Effect 2, who operate under a very similar philosophy.  That Renegade Shepard also displays occasional xenophobic views and tendencies (another major part of Cerberus' MO) is likely another reason for this.

Though occasionally justifying him/herself by claiming that they are doing what is "necessary" this claim loses much of it's validity in the face of Paragon Shepard's consistently being able to find a better way and also Renegade Shepard's hypocrisy. Throughout the games Renegade Shepard expresses disgust at the actions of others even though most if not all of the time these individuals crimes are no worse than what Renegade Shepard themself has done. An example of this would be Renegade Shepard's criticizing rogue Spectre Tela Vasir, even though her loyalty to the Shadow Broker is little different than Renegade Shepard's own loyalty to the Illusive Man. Also noteworthy is the fact that though Renegade Shepard seemingly approves of Cerberus, they are also quick to assume the worst of their so-called allies. This is the opposite of Paragon Shepard, who ironically despite hating Cerberus also sometimes shows them the benefit of the doubt. 

Mass Effect 3

Though always unpleasent and brutal, Renegade Shepard becomes noticably worse in the final instalment of the trilogy, something that did not go unnoticed by many fans, with even people who had up to that point argued against Renegade Shepard's villain status admitting that he/she had become genuinely terrible.  In the third game Renagde Shepard betrays and murders old allies (such as Mordin Solus and Urdnot Wrex), murders Samara's last surviving daughter after Samara commits suicide to keep from having to execute her, and condemns at least two and as many as four sentient species to extinction (the Krogan, Rachni, Quarians, and Geth). Following many of these things many fans outright admitted that Renegade Shepard had established themselves as someone who could not be redeemed, with the Moral Event Horizon crossing in question likely being their cold-blooded murder of Mordin Solus when he refuses to help Shepard sabotage the cure to the Krogan Genophage, itself an act that condemns the Krogan species to extinction. 

List of some of Renegade Shepard's evil deeds throughout the trilogy

1. One of Renegade Shepard's possible backstories is as a war criminal known to Batarians as "The Butcher of Torfan".
2. On the planet Feros, after the colonists of Zhu's Hope become possessed by the mind-controlling Thorian plant Renegade Shepard slaughters the entire town's population just for being in their way even though there was a non-lethal way of neutralizing the mind-controlled colonists that Renegade Shepard chose to completely ignore.
3. Executed Shiala even though she was not really evil but rather just being controlled by the Thorian and before that Matriarch Benezia
4. Betrayed Gianna Parasini (who had offered to help Shepard in exchange for helping her expose a corrupt official on Noveria) and got her killed. 
5. Condemned the sentient species the Rachni to extinction by killing the last Rachni Queen even after learning that the Rachni were a peaceful race and only waged war with the galaxy previously because of misucommunication.
6. Allowed the Citadel Council (and everyone else on the ship The Destiny Ascension) to die even after everything they had done for Shepard. Renegade Shepard can also admit that their actions were motivated by xenophobia.
7. Casually throws their lot in with Cerberus (known terrorists and mass murderers guilty of many ethically sketchy acts and having expressed xenophobic views) and unlike Paragon Shepard (who only pursues an alliance because it is necessary) Renegade Shepard is very comfortable working with individuals who have a similar world-view as them.
8. During Thane Krios' recruitment mission Renegade Shepard mercilessly guns down a clearly traumatized and unstable Salarian who points a gun at them without even trying to talk them down (which Paragon Shepard does). 
9. During Zaeed Massani's loyalty mission Renegade Shepard lets innocent people burn to death just to allow Zaeed to get revenge on Vido, also showing no remorse or concern for the innocent's lives whatsoever. 
10. Encouraged Garrus Vakarian to murder Sidonis in retaliation for his betraying Garrus even though Sidonis is clearly remorseful over his actions and Garrus' killing him will serve no true purpose.
11. Betrayed his party member Samara (who had sworn an oath of loyalty to him beforehand) and allowed her sociopathic and sadistic daughter Morinth to kill her. Shepard also coldly justifies this by deciding that Morinth "is more useful". 
12. Exposed Tali'zorah's deceased father as a war criminal, ruining his reputation and name forever even after Tali begged them no to. 
13. Allowed Project Overlord to continue despite it's being blatantly unethical. This becomes even worse if Renegade Shepard has already recruited Legion and from that learned that the Geth as a whole are not a threat to the galaxy and therefore Project Overlord is a complete waste of time as well as being morally wrong. In effect therefore Renegade Shepard is allowing an innocent man to continue to be tortured for no reason at all.  While Renegade Shepard does express some disgust at what they see, this does little to redeem them given how by this point Renegade Shepard has committed far worse crimes, rendering their disgust completely hypocritical. 
14. Committed genocide against the Geth Heretics even though they could have been reprogrammed instead of destroyed. Renegade Shepard also offers little in the way of justification for this beyond paranoia. 
15. Allowed Cerberus to take the Collector Base, despite it's potential for misuse. This would give Cerberus Reaper technology. More impotently the base was a death-camp where millions were killed to construct a Reaper ship; this leave open the possibility of Cerberus killing millions more to finish the ship's construction.  Renegade Shepard also betrays their so-called allies Cerberus very shortly after doing this.
16. In the Arrival DLC Renegade Shepard commits genocide against the Batarians. Now while Paragon Shepard does the same thing, they do it only because it was the only way to stop the Reapers from entering the galaxy then and there and there was no time to warn the Batarians. Renegade Shepard however, expresses no remorse over their actions whatsoever and their well-established xenophobia also makes their motivations for committing the genocide very suspect. 
17. Sabotaged the Genophage Cure, which condemns the Krogan to extinction. In the process of doing this Renegade Shepard also betrays and murders either Mordin Solus (a former party member) or Padok Wiks. Renegade Shepard can also betray and murder another former party member in the process of this, Urdnot Wrex, and beforehand also lies to Wrex's face when confronted with the proof of their betrayal. 
18. Murdered Samara's last surviving daughter, also rendering her earlier sacrifice if it occurs meaningless. No solid justification for this act is ever given, and it is essentially wanton cruelty. 
19. Possibly condemns the Quarians, Geth, or both to extinction. 
20. Possibly chooses to take control of the Reapers and use them to enforce their desires on the rest of the Galaxy. If the Control Ending is chosen and Shepard is a Renegade, they explicitly make clear that they will put a stop to the "petty squabbles" of the many. 
21. Possibly chooses to destroy the Reapers, in the precess wiping out the Geth and what's left of the Reapers previous victims, even tough he can render the Reapers harmless by taking control of them. Each Reaper is based on, and contain the minds of the spaces that was used to construct it. The energy wave that destroy the Reapers also destroys the Geth. Without the Reapers to keep the Leviathans (Proto-Reapers) in check, this possibly leaves the galaxy vulnerable to Leviathan conquest and indoctrination.

Trivia

Renegade Shepard is quite similar to a large number of their enemies, which in turn makes any disgust Renegade Shepard displays towards them completely hypocritical.

• Saren Arterius: Both are corrupt Spectres with clearly expressed xenophobic views who have murdered large numbers of innocents in the name of said xenophobia. Renegade Shepard like Saren also doubts whether or not the Reapers can really be stopped and can also ultimately choose to do what Saren wanted all along: fuse organic life with technology
• The Illusive Man and Cerberus in general: Like The Illusive Man and his organization, Renegade Shepard is a ruthless and amoral xenophobe who believes in doing whatever is necessary to get the job done and further humanity's agenda, no matter who has to suffer for it.
• Tela Vasir: Both are corrupt Spectres who serve someone other than the Council and help further their agenda without hesitation, justifying their actions as being "necessary" for the "greater good' but really just being amoral sadists.
• Kai Leng: Both are former N7 Marines who come to be dedicated followers of Cerberus that also display homicidal, ruthless, bloodthirsty, sadistic, and xenophobic tendencies. 
• The Reapers: Like the Reapers Renegade Shepard is a genocidal xenophobe who is also an organic being augmented with technology and gets others to follow them and obey their orders against their better judgment. This particular similarity becomes especially noteworthy if the player chooses to control the Reapers at the end of the trilogy, which causes Shepard to become an actual Reaper.
• Shepard's clone: They have same DNA and similar skills, are both xenophobic, manipulative, ruthless, and are fairly self-absorbed. 
• In a non-Mass Effect comparison, Renegade Shepard also bears some resemblance to Ugandan dictator Idi Amin. Both claim to be dedicated and noble patriots but are ultimately just genocidal xenophobes and hypocrites who abuse and mistreat everyone around them, even friends.