"Hitler" almost never appears per se, being an already very rare variant of "Hiedler," but variants such as that, "Hiller," "Hidler," and "Hibler" are. "Adolf" (and its slightly less stigmatized variant, "Adolph") is still seen, especially in period pieces, to evoke a kind of Retroactive Recognition.
Averted: In the children's book Heidi, written long before World War II, Heidi's kind, lonely grandfather is named Adolf.
Adolf is actually used in the novel Evil Genius. One of the villains is named Adolf Hauser. To make matters worse, he's actually nicknamed "The Fuhrer" and teaches at the Axis Institute, a school for future supervillains. May be a case of Refuge in Audacity. Oddly enough, he's not the Big Bad.
Distortions of Hitler's name, especially "Hiller", are featured in works ranging from Who's the Boss? to Isaac Asimov's The Martian Way. In these cases, these people are shown to be Hitler Expys either in-universe or by Word of God.
There is a clothing line called Adolfo that was created by Adolfo Sardina.
Interestingly, Dolph is Jewish. He's even in Hebrew school.
Also, one of Mr. Burns' vicious hounds is named Hitler. Ironically, when seen, he's a very old dog, and not vicious anymore, although Mr. Burns fondly remembers when he was young and "bagged his first hippie".
Dolf The Crow, the sort-of Big Bad from the Dutch TV-Show Alfred J. Kwak was a halfbreed of a crow and a blackbird, spoke in a German accent, turned evil, started a political party with a banner obviously similar to the Nazi flag. He also attempts world domination a few times, and all this while wearing a Napoleon-like attire.
The original Brutus (Lucius Junius), who ousted Tarquin the Proud, and his descendant Brutus (Marcus Junius the Younger), who betrayed Caesar. At the time, the name only meant "stupid" (or by the latter's time, "icon of democracy"), without the connotations of cruelty it would take on in later centuries.
Fallout 3 has a unique Ripper chainsaw named Jack.
Metal Gear: Raiden, whose first name is Jack, was called "Jack the Ripper" during his days as a (very effective) child soldier during the First Liberian Civil War. In Metal Gear Rising: Revengeance, he succumbs to his repressed bloodlust and rage, which unlocks "RipperMode" in-game, increasing damage dealt and causing every attack to break armor and dismember enemies.
Lucrezia Borgia is a character in Gregory Maguire's novel "Mirror, Mirror".
In Going Postal, Adora Belle Dearheart's stiletto shoes are in a style called "Pretty Lucrezia." It fits the trope despite not being the name of a person, because she uses them to attack a drunk (and in The Film of the Book, Moist himself, with whom her relationship is more Slap-Slap-Kiss than in the novel) and delivers a line about how she doesn't know if she can press them straight to the floor, but is willing to try.
Might not sound like a threatening name, unless you happen to have studied the French Revolution, where the original was the guy in charge of the original Reign of Terror. You know, where they chopped off all those people's heads.
Grell Sutcliff of Black Butler has a slightly altered version of the surname of Peter Sutcliffe, also known as The Yorkshire Ripper. Appropriate, considering Grell is one half of this universe's version of Jack The Ripper.
Marilyn Manson's "gimmick" for stage names was to take the first name of an iconic female sex symbol and the last name of a notorious Serial Killer and combine the two. In his case, he combined Marilyn Monroe with Charles Manson; the rest of his original band (which was called Marilyn Manson and the Spooky Kids) did the same. (The stage names of the original members who did this were Daisy Berkowitz, Olivia Newton Bundy, Zsa Zsa Speck, Madonna Wayne Gacy, and Ginger Fish. Members who joined after that did not do so, but Manson's current bassist/guitarist, Twiggy Ramirez, dis so.