Never Live It Down / Transformers

• The Optimus Prime deaths. Each incarnation does die once or twice, and that's once or twice more than most characters who aren't from superhero comics, but you can't say "he's died a million times" unless you treat all Optimuses (Optimi?) as if they were the same guy.
• Ultra Magnus is only remembered by fans for the infamous movie line, "I can't deal with that, now". Not only has it become an internet meme, but it also forever painted Magnus in fans' minds as an arrogant and lazy commander who would rather pass off responsibilities to his subordinates than actually get his own hands dirty. The fact that he's seen coordinating strategies more often than he is executing them doesn't help matters much, but he is more proactive than this misconception paints him as being. On top of that, the original line was said as he was in the middle of trying to pilot a ship that was being chased and fired upon by the enemy, so it was less "Who cares?" and more "Kinda busy here!"
  • Also, from the Transformers Movie, Ultra Magnus "usurps" leadership of the Autobots to the point of insisting the Matrix be merged with his spark, despite Optimus Prime flat out naming Magnus as his successor, and insists that Magnus take the Matrix - Magnus, for his part, even says he's not worthy of it. "Evidence" of this is shown by the fact that the Matrix only glows in the hands of Hot Rod, but because Ultra Magnus is the de facto leader at the moment, everyone just ignores it.
• Remember how G1 Red Alert was always panicky and ultra-paranoid? If so, that makes one of us: In the aptly-named episode "Auto Berserk", when a missile hits him in the face, resulting in brain damage that would have killed him eventually, he starts acting in this manner, to the point of helping Starscream get his hands on a superweapon just to keep the Autobots, whom he believes have turned against him, away. He's fixed later. Fans seem to forget both that he was this way for one episode only due to damage, and quite how dangerous the paranoid schizophrenic Red Alert really was. A mild case of Older Than They Think: Red Alert's toy bio does indeed describe him as hugely paranoid (and his job is head of security during a war - at least a little paranoia is practically a necessity); it's just that this bio was the only time he was ever characterized as such in 80s media. Toy bios were written (and often toys released) in advance of the characters turning up in related fiction and sometimes bore little resemblance to how the characters were portrayed in the cartoon or comic (Ratchet is described as a party animal, for example). Red Alert's paranoia was used for his Day in the Limelight episode but treated as a temporary state of affairs and ignored elsewhere.
• Mix-Mix-Mixmaster's Verbal Tic of re-re-repeating the beginning of a sentence... some-some-something he only actually did in one ep-ep-episode ("City of Steel"). Thank-thank-thankfully. Shrapnel, however, really did repeat the last word of every sentence almost every time he appeared, appeared.
  • Beast Wars once had a damaged Waspinator think he was Shrapnel... only to start talking like Mixmaster did in "City of Steel".
• Hot Rod/Rodimus Prime probably would have been the Replacement Scrappy in any case, given how beloved Optimus was, but he really didn't help his case by being partially responsible for Optimus' death, distracting him at a critical moment, with fans insisting he did it deliberately. But with how it went down, with Optimus failing to finish off Megatron when he has a clear shot and thus giving him the opportunity to grab a hidden gun, while Hot Rod could have done a better job of helping, if he hadn't intervened Optimus would have died anyway.
• In the same movie, there was Soundwave not lifting a finger when Megatron was Thrown Out the Airlock by Starscream, and even veering for the role of leader of the Decepticons straight afterwards, which left something of a tint on his Undying Loyalty persona (which ironically was in full display just beforehand when he carried Megatron into Astrotrain in the first place). This has led to fan interpretations of Soundwave being as ambitious and opportunistic as Starscream (if far more shrewd about it) and only playing a loyal follower until the perfect time comes to usurp his leader, even after Word of God gave a logical explanation for his behaviour (had he won, he'd have ordered Astrotrain to go back for Megatron, before giving his newfound leadership back to him).
• Cliffjumper is remembered by fans as the tougher, red-colored Palette Swap of Bumblebee who's only there to die just to show how dangerous and evil the Decepticons are. This is despite the fact that Cliffjumper didn't have that many deaths to begin with. At best, he's had two major deaths, with everything else being in events that killed off a large number of characters, and he's never died in a decent number of continuities, even surviving the notoriously kill-happy The Transformers: The Movie. But these two deaths occur in Transformers: Prime and Bumblebee and it just so happens they are similar in many regards (occurs fairly early, done to establish the Decepticon threat, and the only major instance of an Autobot being Killed Off for Real)—so similar that fans are now just waiting for another iteration of Cliffjumper to bite the dust. It didn't help that his death in Bumblebee happened only a few months after his death in The Transformers: Unicron, which caused people to think it was in the same mold when it was nothing like the other two deaths (Cliffjumper had been pretty much irrelevant for the entire Phase 2 era, it happens at the end of the continuity, it's not shown onscreen and isn't treated as anything significant, and the miniseries killed off something in the range of twenty or thirty named characters).
  • Similarly, Cliffjumper didn't start off as a Palette Swap of Bumblebee. Cliffjumper's vehicle mode is a Porsche 924 Turbo rather than a Volkswagen Beetle like Bumblebee. The confusion was likely the result of both Bumblebee and Cliffjumper toys coming in red and yellow color schemes (in an attempt to make the toyline seem bigger), and the fact they share the same transformation schematics despite their different molds. This misconception eventually bled into Hasbro itself, who proceeded to make Cliffjumper as their go-to Autobot for a Bumblebee redeco/retool toy with only occasional attempts to give Cliff a unique mold like in Transformers Prime. Eventually, IDW's Transformers (2019) embraced this fandom notion, with an issue dedicating to Cliffjumper's Day in the Limelight as an Autobot who lives in Bumblebee's shadow since the day he was (accidentally) forged.