In the animated movie Justice League: The New Frontier, aside from Superman obviously being the last Kryptonian (as is fairly usual), this actually happens to Wonder Woman when The Centre attacks Themyscira on its way to America. She is the only survivor, making her the last Amazon.
And of course, J'onn Jonnz is the last Martian.
In Megamind both the titular villain and his nemesis, Metro Man are a case of this. Hilariously enough, they met on the way to Earth as babies, and as Megamind put it "our glorious rivalry began".
Manny the mammoth from the Ice Age series. It's merely implied in the film, where he's the only mammoth seen, but in the second film he worries greatly about being the last one. Until he meets Ellie, another mammoth who thinks she's a possum. He attempts to get her to realize her true species. At the end of the film, they discover there are more mammoths besides themselves, so neither are the last of their kind.
They get a baby in the third movie, thus hinting at the chance that they may restart their species.
In Rio, Blu and Jewel are the last Spix's Macaws. They manage to have three children at the end of the movie.
The sequel averts this when more are found in the jungle, including Jewel's father.
Attempts to avoid this trope formed the plot of Pixar's now-cancelled film Newt, which was cancelled for its similarity to Rio.
Disney's Dinosaur features Baylene, the last of the brachiosaurs glimpsed in the movie's prologue. There's a reason for it: the movie is set on the Cretaceous, when the species was already extinct. Meanwhile, Aladar and his family of Plio, Yar, Suri, and Zini are the last survivors of Lemur Island, and the mammals believe themselves the last lemurs until the epilogue when Zini discovers a clan in the Nesting Grounds.
Kung Fu Panda plays this with Po, the only apparent panda in a village of rabbits, geese, and pigs. The second film shows that his kind was killed off by Lord Shen and his wolf army. Subverted in the Sequel Hook. Not only is Po's real dad alive, Kung Fu Panda 3 reveals that there's a village of about thirty to forty pandas with the children outnumbering the adults.
At the end of the original animated film The Lorax, the Once-ler gives the very last truffula seed to the young person he's been telling his story to, along with the duty to grow a new forest and subvert this trope.
In the original short film 9, 9 is the last surviving stitchpunk. In the feature he's not, but the scientist who created the stitchpunks is implied to have been the last human.
It is heavily implied throughout How to Train Your Dragon and the sequel that Toothless, the dragon in question, is the last remaining Night Fury in existence. The third film confirms this, with its main antagonist revealed to have been responsible for the deaths of all Night Furies (except for Toothless). In the epilogue, Toothless and the Light Fury have mated and produced three Night/Light hybrids, partially reviving the breed.
It is implied in The Incredibles that with every superhero having been a murdered by the Big Bad, Frozone and the Parr family are the last of their kind.
The sequel subverts this in which a large number of supers were discovered, including but not limited to Brick and Void.
The main character of WALLE is the last functioning member of his production line on Earth.
Draco in Dragonheart is the last dragon. In a less literal example, his nemesis-turned-friend Sir Bowen is the last Knight of the Old Code. Thanks to the sequel, this title has passed onto his son, Drake. The film also introduces Griffin, an evil dragon that is implied to have been one of Draco's contemporaries, and who is still living in the sequel on account of ensuing humanity. (This is a retcon; possibly justified in that Griffin is a Chinese dragon [with a non-Chinese name]; it's entirely possible that a dragon living in the British Isles may not know about him.)
The low-budget but still enjoyable movie The Last Man, basically. Well, almost.
Jen in The Dark Crystal is under the impression that he is the last of the Gelflings until he discovers Kira. But even then, they are the only two survivors of their race.
Quorra is the last ISO after the ISO Holocaust The Great Purge in TRON: Legacy. By the end of the film there are none left since she has escaped the digital world and become human
In Peter Jackson's King Kong (2005), it is implied that Kong is the last giant ape on Skull Island: the most telling evidence is a shot of him entering his cave and walking past multiple skeletons of giant gorillas. This loneliness, along with the hostility of Skull Island's environment, accounts for both his ferocity and his need for company, which Ann Darrow supplies.
Furthermore, as stated in the background materials, Skull Island's entire ecosystem is dying because the island is submerging due to geological activity. According to the companion book on Skull Island, the entire island sank not long after the crew's second visit to document the area.
Hits its zenith in The Force Awakens: Luke did try to reform the Jedi Order, but it all blew up in his face when his nephew Ben Solo fell to The Dark Side (along with a few other students) and slaughtered all the other apprentices training under him. In the thirty years that pass between Return of the Jedi and The Force Awakens, Luke has retreated to a corner of the galaxy in anguished solitude in order to ensure he is the last of the Jedi. After he passes away in The Last Jedi, the title is passed to his final apprentice, Rey.
By the end of The Last Jedi, Leia is the last remaining Original Trilogy lead protagonist after the deaths of Han Solo in The Force Awakens and Luke Skywalker in this film. Ironically, Carrie Fisher was the first of the OT leads to pass on, having died in December 2016, whereas Harrison Ford and Mark Hamill outlived her.
In the follow-up, Transformers: Dark of the Moon, it is revealed that Optimus isn't the last one; it was merely assumed he was. This revelation is made by the discovery of Sentinel Prime; Optimus' mentor and father figure, who was thought killed centuries ago, but in reality his ship, the Ark, was disabled and eventually crashed on our moon, whilst Sentinel slipped into stasis. He is reactivated for the events of the film, whereupon the more shocking revelation that he had allied himself with the Decepticons occurs, becoming the film's Big Bad via usurping command from Megatron. Optimus is left with little choice but to kill him at the end of the film, presumably leaving himself as the last Prime for certain.
In Transformers: The Last Knight, Viviane Wembly is revealed to be the last living descendant of Merlin (yes, that Merlin) and the only human left who can command the Staff of Merlin (Actually a Cybertronian artifact keyed to Merlin's DNA)
The quote comes from Pirates of the Caribbean: At World's End where, while Jack isn't specifically the last of his kind, pirates are still a "dying breed" and by the third movie, thanks to the actions of Beckett, are bordering on extinction. Jack doesn't feel like fighting for survival, though, and thinks it might be cool to have the nickname "The Last Pirate". He changes his mind when they encounter the dead Kraken, which was the last of its kind, leading to the above quote.
The trailers for The Last Airbender movie has the narrator mention this trope by name: "He (Aang) is the Last Of His Kind, all that remains of a once powerful nation..."
While not actually portrayed in a film, the production of Schindler's List has one of these moments. Steven Spielberg approached John Williams about composing the score, but Williams conceded that there were better composers for the job. Spielberg's reply? "Anyone who is better is dead."
The docu-drama The Age of Stupid portrays Earth in the year 2055 after runaway climate change ravages the planet. The film is shown from the viewpoint of an unnamed Archivist - the last surviving human on Earth - who laments, "why didn't we save ourselves when we had the chance?", and plays back real documentary footage from 2008, when the film was made.
Vermithrax Pejorative in Dragon Slayer is said to be the last dragon in the world after her young offspring are killed.
This is a plot point in the movie Dogma: Bethany is the last scion of Jesus Christ and is needed to help save all of creation. When she finds this out, she doesn'ttake it well.
Similarly to the Bleach example above, The Last Samurai had Katsumoto as the last leader of the samurai class, while Tom Cruise's character is an "adopted samurai" and the only survivor of Katsumoto's army's last stand. Also, many of the samurai (including Katsumoto) had sons and grandsons who were trained as swordsmen....
The Hobbit: The Desolation of Smaug features Beorn, a shapeshifter ("Skinchanger") who was once one of a great race. He explains that many of his kind were slaughtered by orcs, and the rest were captured for sport. He's the only one to escape, and still wears a shackle on one hand, apparently in remembrance. He doesn't like dwarves, but chooses to help them anyway because he hates the orcs that are after them far more.
In Godzilla (2014), Godzilla is described as the last of a species that lived when the Earth's surface was still being heavily bombarded by radiation, as are the MUTOs.
Wonder Woman (2017): The God of War, Ares, slaughtered the rest of the Greek Pantheon, leaving him and his half-sister Diana as the only living gods on Earth. After Diana kills Ares, she is all that remains.
In Kong: Skull Island, Kong is the last of the giant apes. This is bad, since the apes were the protectors of the island's native human population.
David, the eponymous werewolf in An American Werewolf in London is the last werewolf, which becames an important plot point as every person killed by a werewolf since the dawn of time is unable to rest and stays as a spirit on Earth, thus his death will put an end to the curse. Of course, the sequel disregards this completely.
Thanos is the last Titan left in all the universe, as the rest of his species was killed off in resource wars brought about by an Overpopulation Crisis. He's determined to never let anyone else go through this again, even if his "mercy" is perceived as cruelty by others.
By the time Thor, Rocket and Groot reach his realm, Eitri is the last remaining dwarf after Thanos exterminated his entire people.
In Ernest Goes to Camp, it's specifically mentioned that Chief Saint Cloud and his granddaughter are the last surviving members of their Native American tribe.
Hawk the Slayer. Gort, Crow and Baldin are said to be the last members of the giant, elf, and dwarf races, respectively. As you might imagine, the movie is not very original when it comes to character.
Fantastic Beasts: The Crimes of Grindelwald: Leta Lestrange is the last remaining member of the French branch of the Lestrange family. Since her brother Corvus really did die in infancy, with Leta's death her branch of the family becomes extinct. Similarly, Yusuf Kama says he's the last male from his family.
The nameless killer from 1972's Death Line becomes this trope for his subterranean Cannibal Clan after his equally-nameless and bedridden female companion dies.