The Kingpin, archenemy of Daredevil. He's an unabashed crime lord who will ruthlessly eliminate people who hinder his operation. However he almost always keeps his promises, has a fairly strict code of honor, genuinely cares for his friends and family, and treats his underlings well as long as they pull their weight and don't try to backstab him. He actually has a fair amount of respect for Daredevil, if only because Matt so strongly adheres to his convictions. In this regard Kingpin is often contrasted with Daredevil's other archenemy Bullseye, a Blood Knight who commits evil for the fun of it.
Another literal example was the Straw Man, a scarecrow-like demon and one of the Fear Lords: a group of demons who could feed on fear and conspired to conquer and rule the Earth. (The most notorious of them was Nightmare.) The Straw Man eventually double-crossed the others, aiding Doctor Strange to oppose Nightmare. (The reason behind this shift in allegiance isn't known, but it may have been part of its stated goal of taking vengeance upon a group called the Cult of Kalumai.)
Depending on the Writer, this is either played straight or occasionally subverted with Doctor Doom. sometimes he acts like he has a sense of honor, but will do anything to achieve his goals, up to and including sacrificing a woman who loved him to a demon. In other stories, Doom is a man of his word, and keeps his promises, even to his enemies.
For example, in The Amazing Spider-Man Vol. 2 #50, after Spidey has saved Doom from an assassination attempt, he tells Spider-Man that he will repay him for saving his life one day. When Spidey rejected the offer, Doom stated that he immediately repaid the debt by not killing Spidey for his ingratitude.
In a famous storyline from Luke Cage: Hero for Hire, Doom finds Cage in New York and hires him to retrieve stolen Latverian technology. When he finishes, Cage reports back only to find that Doom has closed the Latverian embassy in New York rather than pay the remaining bill. Undeterred, Cage steals one of the Fantastic Four's Fantasticars and flies to Latveria to demand payment. After a scuffle, Doom is so impressed by Cage's audacity that he throws him a wad of bills far in excess of the amount owed.
When Doom does promises, he is also likely to use Loophole Abuse or very carefully chosen words: In a 90s issue of The Avengers, a squad of Doombots took over the mansion. Doom promised that the "real" Doom had a neutron bomb wired into his armor which, if attacked, would kill all the Avengers and most of Manhattan. Eventually they deduced that while Doom was telling the truth about wearing a bomb, he had never entered the mansion, and was sitting comfortably miles away with no intention of detonating.
Magneto may very well define this category, at least when he's on the Heel side of his Heel–Face Revolving Door. He only wants to protect his people and sees a war between mutants and humans as inevitable so he wants to strike first. He may even have a point or two about this, he just can't resist going several steps too far.
Magneto's subordinate Exodus also fits this description, being a centuries-old Knight Templar from the crusades indoctrinated into Magneto's beliefs of mutant supremacy. He sees himself as a knight in Magneto's service and fervently believes in his cause, but his medieval moral code combined with episodes of With Great Power Comes Great Insanity have led him to take actions in the name of mutantkind that even Magneto condemned.
A literal example is Demogoblin, who was created due to a curse placed on the second Hobgoblin, who had previously made a Deal with the Devil. Throughout most of his career, Demogoblin acted like a Sinister Minister, killing people who he believed were sinners, which usually included many Innocent Bystanders. However, in a battle with the actual Hobgoblin, he made a Heroic Sacrifice to save an innocent child who the Hobgoblin had deliberately put in harm's way, dying in the process. This made Spider-Man more disgusted with the Hobgoblin than he ever had been; in the end, the demon who his wickedness had spawned had been nobler than he had been.
Sandman is often portrayed as somewhat heroic, or at least he's only doing super crime for the money. But he has a moral code and is not above teaming up with Spider-Man if the situation requires it.
Venom may be a violent psychopath determined to destroy Spider-Man and anyone who gets in the way of that goal, but he always tries to avoid hurting innocents and tends to go out of his way to protect them. This is because, in Brock's delusional mind, he's the hero of the people and Spider-Man is the monster that New York needs to be saved from.
