Who is the evilest around?
As Kishi has shown us, evil has many faces in the Naruto-verse. It can be hard to say who the most evil character is. So, I would like the opinions of the community. (Note: I will not include characters that do not have their psychology developed, as it would be unfair)
Zabuza: Crazed Swordsman from the mist. Seemingly evil from the start, he killed a massive number of nin and used Haku to his own ends. Ultimately, however, he died an honorable death and was not uncaring.
Orochimaru: Jutsu-obsessed snake man. Betrayed his friends, village, and former teacher, his quest for ultimate power and immortality knew no morality. He frequently deceived and experimented on others including infants. Revealed during the Nagato arc that he had no apprehension about killing youths. In his defense, he was a product of wartime and disturbed by the deaths of his parents.
Hidan: Religious fanatic. It just so happens, however, that his religion deifies death. A seeming sadomasochist, he is very pleased about killing others and injuring himself. He used forbidden techniques and achieved a strange sort of immortality.
Sasori: Impatient puppet man. He betrayed his village, used and manipulated others, and sought to preserve himself through a puppet. In Akatsuki, he worked with Orochimaru. He fought against his grandmother and left Kankuro for dead. However, he died honorably and revealed the truth about Kabuto after his death.
Kakuza: Rag doll Scrooge. Unnaturally old, Kakuza is only concerned with money. He does not fight with any profound purpose, and as a result, he uses the hearts of other people to fight for him. He betrayed his village, although the village was very ungrateful to him for his sacrifices as a ninja.
Danzou: Control FREAK. Leader of Root, Danzou micromanages the flow of information in and out of Konoha. He is distrustful of the other Root operatives and seals their tongues, he killed that frog, and keeps information from Tsunade and Hiruzen. He seems to be affiliated with the village elders, but he also will work with Orochimaru to access power and forbidden techniques. He is a complete utilitarian, but he does work tirelessly to ensure the safety of Konoha.
Madara/Tobi: Ancient avenger. Driven by revenge, the founder of the Uchiha, Madara has a strong belief in maintaining his clan and also attaining a uniform world. Unfortunately, he seeks these goals through violence and control. He uses the power of potentially violent and insane Akatsuki members to reach his ends.
Deidara: Spontaneous explosion. Much of what Deidara does is in pursuit of his artistic vision. He is able to put any feelings aside, so long as his actions have explosive results. In an extreme case, he endangered the lives of the entire Sand village during his fight with Gaara.
Tsuchikage: Old grump. The Tsuchikage is an outdated old man who is hesitant to fight, due to his frail body, but also maintains that he should be respected. He has used, and therefore funded, the Akatsuki organization for the purposes of maintaining his land's power. He does not trust individuals and lectures often. Moreover, he is unwilling to work with other villages if he is not in control.
Jugo: Gentle killer. Jugo was born with a transformation in him. The other side of Jugo is a psychopathic killing machine. However, even the bad side of Jugo can often be pacified, and in the case of the Kage Summit, he did not turn and attack his teammates, and this was when he was fully transformed.
Raikage: Stubborn hothead. The Raikage is self-destructive, both physically, and in terms of attempting to make a peaceful ninja world. He does not attempt to stop the cycle of revenge, as is shown when he tries to kill Sasuke. However, much of his motivation stems from a love of his brother and his village.
Sasuke: Power hungry hater. Sasuke has been a character that we have seen develop from a normal child, into a gifted nin with slight arrogance, into a revenge motivated killer. Sasuke betrayed his village in his quest for more power, and he has continuously refused to stop, even after finding out that the bane of his existence, Itachi, was trying to protect him.
Itachi: Protector traitor. Itachi was a lifelong pacifist, until he was forced into a utilitarian moral question by Madara. In order to prevent war, which Itachi despised, he performed the heinous act of killing almost the entire Uchiha clan. He spared his brother and tried his best to protect him from further evils.
Tailed beasts: Agents of destruction. The tailed beasts are frequently portrayed as sentient animals that are aware of their actions, but cannot be held responsible. As Bee demonstrated, the tail beasts can be made into allies. However, the vast majority of the tail beasts have seemingly attacked without discretion.
Minato: He sealed the Kyubii in his own son! Damning Naruto to a lonely childhood and a life of being hunted and feared. However, he left his spirit inside his son to help guide him and believed in the strength of Naruto (just trying to be fair about who I call evil ).
Pain: Genocidal pacifist. He killed an entire village with the reanimated corpses of fallen ninja. He kept his village under strict surveillance and made it a miserable rainy place. However, he did his best to fix his mistakes, and he did it all, like Madara, for his vision of peace.