The best example for this is ( that i can think of) is probably Vlad III of Wallachia (Vlad the Impaler). As you probably know, he was a cruel leader that ruled with an iron fist and killed ruthlessly any opposition from the boyars ( the nobles of Wallachia) : hanging, burning, boiling alive and of course impaling. I won't go into too much detail about his life or his reign, but what you need to know is that he was put into power by the ottomans ( he and his brother were sent to Constantinopol as kids by Vlad II of the Dragon,his father, where he lived all his youth) because they thought he would be sympathetic towards them, as he lived among them all his life. But this backfired hard as he had a deep hatred for the ottoman empire because, as he saw it, they kidnapped him as a kid and betrayed his father. This resulted in him going to war with the ottomans, while succesful at first, it resulted in him fleeing into Transylvania (then under hungarian rule) and the ottomans tightening the noose around Wallachia by doubling the tribute and taking a more direct aproach towards the country's leadership.

What a lot of people don't know is that Vlad is regarded as a national hero in Romania, the cause of this is because in the 19th century, with the surge of nationalism across Europe after the 1848 revolutions (The romanian principalities : Wallachia, Transylvania and Moldavia also had an uprising, demanding the unification of the countries under one flag : Romania,but it was crushed by the Austrian-hungarian and the ottoman empires) a new cultural movement appeared in the romanian principalities, it was called the "pasoptist" movement ( after the romanian spelling of '48 : patru zeci si opt) that glamorised a lot of past rulers as heroes of the nation, presenting Vlad as a hero that cracked down on corruption and fought against the ottoman oppressors through glamourous poems and paintings

Sources : Florescu, Radu R.; McNally, Raymond T. (1989). Dracula, Prince of Many Faces: His Life and his Times. Back Bay Books Florescu, Radu R. (1991). "A genealogy of the family of Vlad Țepeș"

edit: corrected a mistake where i called Vlad the II instead of the III

This is going pretty far back but another example would be Emperor Nero. Obviously, he is one of THE notorious bad Roman emperors. And the contemporary or near contemporary historians are relatively uniform on that. Although Tacitus notes that while the senators and the upper-class welcomed his death the common people were less enthusiastic.

But here's the thing. There was a very long lasting folk legend surrounding Nero that he didn't die and would return or that he would come back reclaim his rightful place. Augustine of Hippo claimed some still believed this during his own lifetime (Nero died in 68 and Augustine lived 354-430.)

There were several revolts led by men purporting to be Nero that found popular backing. We don't have a lot of detail about why this was the case but it seems he had popular support among the people. Especially in "the East" (which is Greece.)

Tacitus notes that the common people were supported by Nero's excess, meaning they enjoyed the games and grain he provided regularly. During the famous Great Fire, which most of the ancient historians blame on Nero directly, Tacitus (who is unsure whether Nero was responsible or not) notes that Nero rushed back to Rome to handle relief efforts. And he provided shelter and food to those devastated by the fire. All of his own funds. There is a lot of evidence that the popular perception differed strongly from the Senatorial perception of the man. While the Senatorial class wrote history, we have the echos of this from that folk legend that took centuries to die.

Hugh Trevor-Roper has written a lot of essays about the seventeenth century and the construction of history, and one of his favorite topics is "Good Queen Bess".

The sixteenth-century reign of Elizabeth I of England was indeed a prosperous time, even a Golden Age for England. And Elizabeth has gone down in history as a great and beloved monarch ("Good Queen Bess" and "Gloriana" are, let's face it, much better nicknames than "Bloody Mary").

But to a large extent, "Good Queen Bess" is also a creation of seventeenth century political writers. Those who were discontented with the Stuart kings pointed to Elizabeth as the standard of benevolent monarchy. Good Queen Bess, they said, did not insist on tyrannical absolute power over the Commons. Good Queen Bess was not a crypto-Catholic! Good Queen Bess did not allow the Puritans to gain power! Now of course, this does not have anything to do with Elizabeth as an actual monarch; rather, the best parts of her reign and the most desirable parts of her public persona are being appropriated for contemporary rhetoric. And later on, when the civil wars came, many people could speak longingly of the prosperous days of Good Queen Bess, when England was powerful, wealthy, and rich, and "those people" were not in power. In the 18th century, political conservatives could still refer to Elizabethan England as a Golden Age.

In the 19th century, when there is a great aesthetic revival of medieval and Renaissance art and architecture, the idea of "Merry England" becomes popular. "Merry England" is another historical reconstruction of a lost Golden Age when Things Were Better, More Romantic, More Adventurous, More Fun (the idea of "Merry England" actually dates back at least to the Reformation, but has a wave of popularity in Victorian times.) Again, the idea is to recapture a lost Golden Age, but if the Middle Ages are a little too Catholic, and the Stuarts are a little too tragic, (and Henry VIII is a little too cruel), then Good Queen Bess is always there to preside, in the imagination, over historical adventures and pageantry.