In the era of Super, there's little doubt Vegeta became a much better person, having saved the life of a Namekian child from Moro, shown serious regret over his past, and restored many Namekian lives taken by Moro through his spirit fissure technique as an act of penance. But before Super went into publication where he would undertake more serious acts of atonement, he was mostly a Nominal Hero who got romanticized despite destroying planets, ordering the deaths of almost all the Z-Warriors, beating up children, slaughtering innocent villagers and spectators, endangering the lives of his allies and the Earth just so his ego could be satisfied, and killing his comrade Nappa who, while not a good person himself, had been Vegeta's caretaker and companion since childhood. Back then, both English dub and his fanbase excused or downplayed his many controversial actions, blaming Vegeta's cruelty on the years he spent as a servant under Frieza (whereas in the original manga the only grievance Vegeta had with Frieza was that he had to kowtow to the emperor's will). Ultimately, after many years both in canon and real life publication, Vegeta himself would dismiss the idea it was Frieza's fault when he acknowledged during a moment of serious self-reflection during the Grandolah Arc that Frieza wasn't to blame because the Saiyans had many ruthless and evil qualities before they even served under the Galactic Conqueror.
King Vegeta, who's shown no remotely positive characteristics other than a royal posturing habit and an English dub voice that could pass for a half-assed Major Armstrong impersonation, gets planted with this status just for going after Frieza. Generally, the best way to get on this list with the DB fandom is to rebel against your Eviler than Thou boss.
Piccolo gets this, despite not being a villain since the start of the Saiyan Saga. Goku putting Gohan in the Cell Games is a big Never Live It Down moment for him within the fandom. He put his 11- (9 in the manga) year-old son against a killer android when Gohan didn't have the love of fighting like Goku and it took Piccolo pointing this out for Goku to understand the problem. The thing is, Piccolo did the exact same thing in the Saiyan Saga. He kidnapped Gohan and trained him to fight against two genocidal aliens when Gohan was only 5 and had no battle experience. He then chewed Gohan out to the point of tears when he was too scared to fight effectively. The fandom is getting on Goku's case for something Piccolo gets a free pass on.
Bardock. Holy cow, Bardock. Fans of him tend to overlook the fact that he made a living by slaughtering BILLIONS of innocents so their planets could be auctioned off. The Funimation dub doesn't help, either, since it portrays Bardock as being a "repentant sinner" whose rebellion against Frieza was his atonement, when originally he was simply pissed that Freeza was going to kill the Saiyans. The Episode of Bardock special further made him a good guy (though its canonicity is dubious). Even Toriyama got in on the fun through Dragon Ball Minus, in which Bardock is seen showing much more concern and acceptance towards both Kakarot and his White Sheep wife, Gine. At the same time, the first panel of him is him slaughtering a group of aliens with a huge smile on his face.
Actually, just being a Saiyan of note can get you on here. Raditz gets this for being Goku's brother (and Goku giving him this treatment for five seconds), Nappa gets this in large part due to the fun factor potential in his brute character being exposed by Team Four Star, and Broly gets this on account of basically being the Hulk as a heel in permanent on mode (it doesn't help that his canon incarnation in Dragon Ball Super: Broly is far more sympathetic than his original characterization was). Female Saiyans like Fasha of course get this be default since they are prime Fan Art and Fanfic Fuel.
Cell also counts since he tends to fall into the Alternative Character Interpretation. There are also those who downplay his actions, saying that Cell just wanted to get stronger, test himself, and have a fun tournament, which makes him no different than Goku. This is ignoring that Cell literally ate cities, tortured the Z-Fighters, crushed Android 16's head for no real reason other than to be a dick, and mocked Goku's Heroic Sacrifice. Cell also freely admitted to wanting to terrorize the Earth once he defeats everyone in the Cell Games, all so he can enjoy the looks of horror in people's faces.
Dragon Ball Super: Frieza has definitely become this here, especially in the Universe Survival Arc. Most of his fans see him not only as the embodiment of Evil Is Cool, but also more sympathetic than he was in Z. Some even have a disturbing habit of justifying Frieza's past actions, no matter how flawed the excuse is. Of course, this is ignoring that Frieza shows zero regret for his actions and even rejoices in remaining evil. Ask anyone who has seen the end of the Universe Survival Arc. Most will answer you that Frieza is a true hero, incredibly badass and amazingly cool. His moral ambiguity at the end of the Arc has opened an endless debate between fans.
Dragon Ball Z Abridged sometimes does this with characters, although generally it's less to do with what they think of a character and more what helps them write funnier jokes. The most notable examples being Nappa, who does the same things he does in canon but comes across as Obliviously Evil, Dr. Wheelo, who was potrayed as a evil Mad Scientist in the original The World's Strongest but here is a kind-hearted cancer researcher who barely does anything evil and gets Spared by the Adaptation, and even Dr. Gero, who, while still evil, is given a more sympathetic motive when it's revealed that Goku had killed his son.
