If it isn't undone, at least we can take comfort in that it came late enough in the game for everyone to remember the original state of the character.
And sometimes, this trope happens.
This is when Character Derailment becomes the new status quo for the character. The Derailment lasts so long that newer viewers/readers/players don't even realize the character has been Derailed at all.
As such, those new viewers are prone to They Changed It, Now It Sucks when the character finally gets rerailed (or shows signs of his/her's actual characterization), while longtime viewers take a breath of relief.
- Machine Man's Derailment in Nextwave sticks even to this day, to the point that few remember that he used to be kind, polite, gentle and friendly (or that his name is supposed to be Machine Man and not "Aaron Stack").
- No matter how hard writers try to revert Jean Grey's characterization back to her noble and heroic self, she seems to be destined to be "Dark Phoenix" for the rest of her existance.
- Originally, Freddy Krueger was characterized as a legitimate menace, and his kills were more direct and efficient. As the sequels passed, his sense of humor overtook not just his character (who became Laughably Evil), but his kills as well (becoming more elaborate and outlandish), and that's how the character is currently stuck as (New Nightmare and the 2010 remake aren't canon and thus have no bearing on the character).
- In post-The Review Must Go On Nostalgia Critic, Malcolm was originally characterized as the Only Sane Man, often offering valuable insight and trying to reign in Critic's destructive tendencies. Over time, this faded away for the Yes-Man characterization that he is better remembered for.
- Despite Erin Winters naming the trope about Flat Characters gaining Character Development that sticks, her characterization in Scary Go Round as a Gentle Giant Lovable Jock ended up fading until she got Derailed, first as "the Queen of Hell", and then as just a non-demonic Jerkass, and because of Scary Go Round ending and Bad Machinery still going on, that's how most new readers see Erin as.
- The Shredder, Bebop and Rocksteady were original portrayed as a legitimate threat in the 1987 show, but they were soon Derailed into Stupid Evil Harmless Villains, and due to the overall more comedic tone of the show, that's how they are remembered as.
- Daffy Duck spent so much time as a Small Name, Big Ego Jerkass that almost nobody remembers his original characterization as a Screwy Squirrel Trickster Archetype.