It was interesting to see Arya mentioned, as so few people ever seem willing to acknowledge her being evil. Even more surprising was that she was beating Jaime Lannister. Of course, placing Cersei on the poll is a bit skewed, since she is far and away the worst of the lot. Of Jaime, Theon Greyjoy, Arya Stark, Cersei, and Robert Baratheon, I'd have to say Robert is the least evil and Cersei the most, by far. I have to wonder, however, if people are being led astray by the PoV trap, since aFfC. I recall discussions of that book on wotmania where people were actually sympathetic to her "plight" and parroting her own opinions that everyone was stupid and inept and betraying her, and she had such a hard life, and no one loved her and she was just trying to protect her kids and her husband was so mean to her and all the other myriad excuses & justifications she offers in her stream of consciousness.

The PoV trap seems to be the likliest explanation for Jaime's escape with so little of the vote. People like to contend that he is changed or reformed, based solely on the fact that he is smart enough to walk a little more softly now that he is no longer one of the greatest warriors in the kingdom, able to slay with impunity amyone who takes offense at his being a dick. As of aFfC, however, Jaime is still conspiring to place an illegitimate pretender to the throne in charge of a kingdom, and in this particular case, it means aiding and abetting Cersei's rule of the kingdom, when he knows better than anyone how bad she has become. He also knows that he could put a stop to it as no one else could. The Lannister swords would almost certainly follow Jaime if he tried to depose Cersei, and as Littlefinger notes, she doesn't truly possess any real power of her own. But Jaime lets it all go. His apparent belated adherence to his vows as a knight of the Kingsguard have as much to do with his superstitious guilt and fear of discovery as any real integrity. His apparent rejection of Cersei at the end of the book has no evidence of being grounded in any moral decisions or realizations, and his entire storyline in that book argues rather that he is casting his sister to the wolves because she cheated on him. His clashes with Cersei in aFfC have little to do with her competence or a burgeoning devotion to duty and morality, but with Tyrion's final words to him in aSoS: that Cersei has been sleeping around.

Additionally, since his apparent reform, he made the charming threat to catapult a newborn baby into a besieged castle to encourage its father to surrender. Lest anyone contend it was not a serious threat or merely a bluff to intimidate the father, recall previously he had derided the Freys for making threats they did not intend to follow through, regarding the exact same man. He is contemptuous of them for threatening to kill Edmure, without actually doing it, but we are supposed to believe that his threat to send Edmure's wife and child to join him via trebuchet is just a bluff he has no intention of following up on?

As for the other characters, Theon also appears to have come away positively with the PoV trap, as the latter part of his story in aCoK was seen entirely through his eyes, and we never got another character's view of his words and deeds. While his attack on Winterfell was justified as an act of war, and it turns out that he didn't kill Bran and Rickon, he DID murder two innocent children to cover up his failure to catch the Stark boys, and later on, murdered his own sworn men to cover up THAT crime. And then he executed an innocent man for the crime he himself committed, and with the idea foremost in his mind that he had to do these things to make people afraid of him and take him seriously, he then threatens yet another child. As in the case of Jaime, his own thoughts on this matter, and past history of atrocities completely undermine the "he's only bluffing" defense.

There is no excuse for Cersei at all. She can scarcely go three pages in her PoV without committing, attempting, planning or desiring some new evil deed. Her imprisonment in the end of the book, which seems to have brought her unearned sympathy IS entirely justified and legitimate. She herself approved of the Faith's jurisdiction in that area, and lest anyone forget, she IS guilty of EVERYTHING of which she is accused, tried to frame other women including apparently innocent underage girls for the exact same offenses, and those crimes are merely the tip of a vile iceberg of atrocities, going back to her childhood, when she abused her brother and murdered her companion to cover up an embarassing fortune. When you consider how many wotmaniacs excoriate Tuon for a brief flash of temper that caused no permanent or lethal harm over the exact same issue, it is not surprising the Cersei tops the evil poll, but it is really hard to believe that anyone else received votes next to her, when she has committed every single crime any of the others have, and more besides. She has betrayed her sworn vassals, her family and her king. She is guilty of murder, assault, terrorism, regicide, treason and tyranny. She has committed every sort of sexual immorality short of child molestation or rape, though the last book saw her regretting her physiological inability to do that last, and no one could credibly make a case that she would balk at such ends if ordering those crimes could serve her ends. There is absolutely no good in Cersei, and even her claim to maternal love is undermined by how she is shown to express that love - it is thoroughly selfish and self-aggrandizing. She does not want the best for her children, and their well-being is a distant second to her own convenience or glory.

As for Arya, the girl is deliberately and willingly seeking employment as a professional assassin! No matter what mendacious tale of mercy or justice the Faceless Men use to dilute the unsavory truth of their occupation, they commit murder for money. Arya knows this, she was raised to hold proper values, and she still pursues a career with the Faceless Men in spite of that. You can make all sorts of arguments about how her losses and harsh experience is driving her to that, but the reasons why a person's character are formed in a certain way have nothing to do with whethr or not they are good or evil. They are good or evil based on their actions and intentions, not on what experience causes them to see evil deeds as an acceptable means. And, too, she murdered Daeron or Dareon or whoever the singer from the Night's Watch was. She was not in the Seven Kingdoms, so their laws do not apply. She is not a bannerman or titled noble with a responsibility or right to uphold the laws of the Seven Kingdoms, no matter what she claims in her assertion that Arya Stark did the deed. Plain and simple, she committed cold-blooded murder, for no genuine reason. He was no threat to anyone, least of all Arya herself, and there is simply no excuse for killing him. This proves that Arya is not simply in denial about the reality or actions of the Faceless Men - she is perfectly willing to commit murder and take lives for which she has no good cause.

Finally there is Robert. He is not quite the bold-faced and bloody-handed villain as the others, but he is perfectly willing to murder a pregnant fourteen year old girl who, as his best friend and chief counselor points out, poses no real threat to him. All the violent intentions and inherited hatreds in the world do not allow an army of light cavalry to cross an ocean and conquer a land thick with fortifications and inhospitable terrain. He forgives and accepts the murderers of children because it brings him power. Even the realpolitik excuses about the threat posed by Rhaegar's children are not a justification for their deaths. Lest we forget, Robert had no genuine claim to the throne, and certainly not a superior right to that of either child! They had done nothing to warrant their murder, aside from exist in circumstances that would deny Robert Baratheon power. People parrot Littlefinger's bullcrap about Eddard Stark being too virtuous and his honor bring him down, but it was really his failures of honor and justice. Had he been truly honorable and just, he would have refused to take part in an administration soaked in so much innocent blood, he would not have rebelled against the entire Royal Family, consisting mostly of children, because the king had to be removed. Rhaegar and Aerys might have had to go, but why does it follow that Viserys, Aegon & their sisters must also be dethroned, so that an oversexed alcoholic can rule? If good and wise men like Stannis Baratheon, Jon Arryn and Ned Stark can counsel Robert to rule justly, why not simply take charge of the children of the Targaryen tyrants and monsters and raise them properly? They knew Robert's flaws and faults even if they had no idea how far they would grow with no one to check him. At that point, no one could make an argument that the infant Aegon shared them and so could not be as good a king as Robert.
And speaking of those flaws, we have the fact that Robert is an inept ruler who wastes the kingdom's substance on his own self-indulgence and is known to be flagrantly guilty of every one of the infamous seven deadly sins. Being a fun guy to hang out with the Westeros equivalent of college does not excuse any of that. It is a mark of his wretched behavior that some readers are willing to excuse Cersei's infidelity and incest, despite his generally positive portrayal and her negative in other character's PoVs (Robert is only seen through the eyes of the Starks while Cersei is seen entirely from the PoV of her enemies until aFfC).

All in all, while they are all evil people, I still think Cersei is the worst, and by no standard should Jaime be the tail end vote getter.