Shado in the original comics was a Japanese assassin who raped Green Arrow. In the show, she's a lawyer and one of Ollie's friends on the island, even training him in being an archer and developing an unrequited love for him. When she is killed, Oliver vows to honor her for the rest of his life by taking on her green hood and cloak as the Hood (later the Green Arrow).
Anatoli Knyazev aka KGBeast. In the comics, he was usually a Psycho for Hire, while on the show he's a sympathetic mobster who helps Ollie during his trip to Russia. He did later turn against him late into season 5, thus being part of Ricardo Diaz's group of criminals in season 6, but sided once more with Oliver near the end of that season.
Merlyn. In the comics, Merlyn is a Psycho for Hire and has opposed the JLA as a member of the League of Assassins and the Injustice League, while on the show Malcolm Merlyn started out as a Well-Intentioned Extremist who wants to destroy the Glades to avenge his murdered wife and simultaneously put an end to the criminal element there that was threatening the rest of the city. He gets better. Merlyn gradually becomes an ally or at least a frenemy of Team Arrow, largely due to him finding out that Thea is his biological daughter as a result of a fling with Moira years ago, and stricken by guilt over the death of his son Tommy during the destruction of the Glades, vows to become a much better father for her than he was for Tommy. While he isn't winning any 'father of the year' awards due to his admittedly ruthless training of Thea and his drugging and manipulating her to kill Sara as part of a convoluted plan to get Oliver to take down Ra's al Ghul, he genuinely cares for her as is exemplified by him weeping when she almost died at the hands of Ra's himself. He was also highly hesitant in supporting Oliver and Barry's decision to not bow to Vandal Savage's demands and deliver the Hawkpeople to them (in return for him letting them, their cities and their loved ones survive) and directly threatened to come after Ollie in case Vandal ended up hurting or killing Thea. He has also come to care for Oliver in a certain way, even admitting that he now sees the latter as another son, though this again hasn't prevented him from occasionally manipulating or generally being a thorn in the side of Ollie now and then.
Slade Wilson (the comics Deathstroke) in the island flashbacks completes the Power Trio with Ollie and Shado. No longer the case as of the present-day scenes in "Three Ghosts", explained away with flashbacks that show he eventually had a Face–Heel Turn to become the more familiar, vengeful supervillain of the comics after taking the Mirakuru formula. Double subverted upon his return in the Season Five finale, where he's pulled a Heel–Face Turn after the Mirakuru was worked out of his system.
In the comics, Ra's al Ghul's daughter Nyssa is a villain who plots revenge on her father by brainwashing her half-sister Talia, and wants to kill Superman in order to destroy hope. In the series she's got a role similar to classic Talia, torn between her loyalty to her father and her love for one of the heroes (in this case Sara Lance).
One of the big complaints about the series by fans is the titular John Constantine, himself, is this. His addiction to magic and meddling with forces mankind was not meant to know is downplayed to, instead, focus exclusively on the Newcastle Incident as his motivation. This version of John is The Atoner and wants to make up for his crimes (as well as avoid damnation) versus the John who is a rebel without a cause. This isn't that far from some comic portrayals of John, albeit significantly Lighter and Softer. Constantine also comes off better in dealing with the below mentioned Gary Lister; in the comic, he doesn't sit by Gary's side so he wouldn't have to be alone while being eaten alive, either.
Chas has an active role in Constantine's good deeds and is fairly competent at helping out even besides his immortality. In the source material, he is more often then not simply roped into the insane things that go on around Constantine, often only to the extent of being press-ganged into being John's driver, and is ill-equipped to handle the supernatural. His wife Rene also gets an upgrade, going from extremely abrasive, controlling and rarely sympathetic to being generally unsupportive but understandably so, considering how things look from her perspective.
Gary Lester is made more sympathetic than his comic counterpart, who was much less accepting of being the host for binding Mnemoth inside of
It's easy to imagine the comic version of Papa Midnite working to fix things when his magic goes off the rails and brings the dead back as ghosts who cause havoc for practical reasons. When this actually happens in the show, however, he seems to have at least some genuine concern for the people who are caught in the middle. Further, in "Waiting for the Man," while he uses his dead sister for information, he also seems to be actively trying to bring her back. In the comics, he not only would never willingly give up her use as a tool, she has to team up with Constantine to escape him.
Gorilla Grodd is a violent sociopathic gorilla who despises humans and attempts to make apes rulers of the Earth with him as leader. While this version still hates humans, two in particular not withstanding, he has an actual reason due to being a guinea pig for psychic experiments and suffered abuse. He finally has a Heel–Face Turn after Crisis on Infinite Earths (2019).
Plastique. In the comics, she was a villain of Captain Atom and a convicted terrorist before making a Heel–Face Turn. Bette here is portrayed as, at worst, an Anti-Villain who fears her powers and wants to get rid of them. The worst thing she does is attempt to kill General Eiling, a Knight Templar who would come after any and all meta-humans to turn them into weapons for the Army, and had to be convinced into doing so by Dr. Wells.
Dr. Harrison Wells, who is secretly the Reverse Flash in disguise and the main antagonist of the first season - is primarily motivated as a villain not so much by his desire to destroy the Flash like in the comics, but by his desire to return to his time and place in the future and reunite with his loved ones - albeit at any costs. In spite of also initially hating and seeing Barry as an enemy to be destroyed in his origin story, he grows to become genuinely fond of the young man and comes to see him as a son, even admitting that it was not his version of Barry he hated but his future self, and that they were never enemies in the first place. Thawne even goes as far as passing S.T.A.R. Labs down to Barry as part of his will in addition to giving him a video-taped confession about his role in murdering Nora Allen, exonerating Henry who was unjustly imprisoned for the murder and whom Barry had till then dedicated his entire life to get justice for. While Thawne is still the man who murdered Nora in the first place, the one who was responsible for framing Henry in the first place and still the monster of the Flash's childhood - it shows that on the show even the Reverse Flash has a heart, at the end of it all. However, later stories would double down on his evil qualities, as he becomes consumed in hatred when Barry destroys his time machine to prevent him from going to the future, and during Crisis on Earth-X, joined the Fourth Reich, later manipulating Barry's future daughter Nora into setting him free and getting RetGoned, then actually killing Barry when he was still a child to try to erase him from reality.
Hunter Zolomon from the main universe is a normal civilian and is not a super villain unlike the comics. On Earth-2, however...
In the New 52 comics, the Future Flash has been driven mad in a Bad Future with crippled and deceased loved ones, and plans on murdering anyone who wronged him in the past. The Future Flash of the show is morose and depressed, but is convinced to return to heroism by his younger self. This is because all of Future Flash's negative traits have been transferred to Savitar, who turns out to be his time remnant.
Oddly enough, Savitar is a retroactive case of this. The comics Savitar was a straight-up supervillain who turned to destruction and crime as soon as he got his speed. The show's version was a genuine hero when he was still Barry Allen. It took losing his parents, watching the love of his life die, and getting ostracized from his friends for him to finally make a Face–Heel Turn.
Hank Henshaw, usually a Superman villain (the Cyborg Superman), is a good guy (which makes even more sense when we find out that he's really J'onn J'onzz, the Martian Manhunter). Eventually averted, as it was eventually revealed the real Henshaw is indeed the Cyborg Superman and works for Cadmus, and J'onn had only assumed his identity after believing him dead.
The Toyman's son in the comics is the supervillain Dollmaker. Winn is portrayed as a genuinely good person. Somewhat justified, as Dollmaker has appeared both in Arrow (as a serial murderer) and Gotham (asaMad Doctor).
The entire planet of Daxam undergoes this. In the comics they're a race of Fantastic RacistAbsolute Xenophobes so despicable that Sodom Yat, one of only two known decent modern Daxamite (the other being Mon-El), refused to save them from Sinestro. Here they're more like obnoxious frat boys than space Nazis, although the Queen of Daxam turns out to be much worse that Mon-El suspects.
