A character that's described as the purpose of life itself. A being that's at the top of the Evolutionary Levels. They're the perfect life form, but what they are tends to vary. Some works have them be something akin to a god, others state that the most adaptable creature would have this title, and in others still, it's nothing more than a simple yet hardy cockroach. A formerly normal person might even become one, usually trough some form of genetic engineering or enhancement.
A variant has the character be at the top of a specific type of life, instead of being the apex of all life as we know it. For example, a perfect human, dog, tree, machine, predator, etc.
There is an incredibly high chance that their appearance looks human(ish).
Also, while the theory of evolution pretty much disproves the concept in real life, there have been claims that certain species or people do indeed fit the description, so adding examples to that section is perfectly fine.
From Fullmetal Alchemist, Father's final form had the power of God. Unfortunately for him, the power put too much strain on his body, eventually rendering him vulnerable to counterattacks.
Cell from Dragon Ball Z, a bio-engineered creature made from DNA harvested from the greatest fighters in the series up until that point considers himself to be this, and says so in as many words.
Tentei (The God of the Heavens) in Twelve Kingdoms; the rulers and officials of kingdoms can err, but this guy certainly can't.
Szayel Aporro from Bleach calls himself the ultimate, perfect being because he has a phoenix-like system of death and rebirth, but you can bet Mayuri proved him wrong. Gruesomely, and with a rant about perfection being the enemy of a scientist.
Betterman: Kankel is described as the final stage of evolution, so much so he has the nickname of "Best Man". His ridiculously powerful abilities help back this claim up.
Ireul from the TV series also heavily fits with the adaption part of this trope.
L-Gaim: Oldna Poseidal fits this description since he's virtually immortal.
The Pillar Men from Jojos Bizarre Adventure are referred to as the ultimate life forms. One of them, Cars, becomes the real ultimate life form when the Red Stone of Asia removes his vulnerability to sunlight and allows him to replicate the abilities of all other life forms.
Andromeda Strain: The titular entity adapts to any situation almost instantly and proves itself to be virtually unstoppable.
Evolution: The basic bacteria that create the alien creatures are described as the most powerful life form. Of course, no one takes this seriously until one grows to the size of a city by absorbing vast amounts of napalm.
God, according to The Bible. YMMV as to whether He counts as a life from, though.
If not God, then in the religions that believe in him, Jesus was sent to Earth to be the perfect human and set the example for us.
The Types (Type-Moon, Type-Mercury, etc.)/Aristoteles in Angel Notes. Each of them is the ultimate life form of their respective home planet or satellite, even if said celestial body doesn't support life (anymore).
In the Hyperion Cantos by Dan Simmons, the branch of the technocore dubbed the Ultimates are working towards the creation of an Ultimate Intelligence.
In The Last Continent, the heroes encounter the God of Evolution, who, despite not understanding what the deal is with sex, believes he has achieved the ultimate life form. It's a cockroach.
Nietzsche proposed in his book Also Sprach Zarathustra that humanity needed to evolve into what he termed the Übermensch (Super-man); that humanity was merely a transitional evolutionary phase between apes and this perfect form of man. Those Wacky Nazis picked up on Nietzsche's theme with their idea of an Aryan master race.
The Star Trek: Voyager episode "Threshold" subverts the "looking human" thing - Paris & Janeway get advanced evolution and end up looking like salamanders. Later subject to Canon Discontinuity though.
The objective of the Borg of Star Trek: The Next Generation is to attain "perfection", both by augmenting their own bodies cybernetically and by assimilating the biology and technology of other cultures.
The "Chaos Effect" line of Jurassic Park toys had the Ultimasaurus, a genetically altered monster created from Tyrannosaurus, Velociraptor, Triceratops, Ankylosaurus, and Stegosaurus DNA to create the ultimate predator.
Arguably, this is the status of the Ultimate Chimera in Mother 3.
The main villain in Parasite Eve attempts to create this and succeeds; this creature is the final boss of the game.
In Chrono Trigger, it's revealed at the end that Lavos' true purpose is to become such a being by parasitizing entire planets and subverting their own evolution to its own ends.
Psaro's Roaring Rampage of Revenge against humanity in Dragon Quest IV leads him to seek the "Secret of Evolution," which allows him to achieve a monstrous One-Winged Angel form with which he intends to exact his revenge against the world. In the PS1 and DS remakes, it's revealed that one of his own henchmen manipulated him so that he could obtain the Secret of Evolution himself.
Tardigrades, also known as "Water Bears", are notorious for being able to survive extreme conditions. To elaborate, they can withstand low temperatures close to absolute zero, high temperatures at 151 degrees celsius, radiation (Even more so than cockroaches), and can even survive for up to ten days in the vacuum of space (Heck, some of them even reproduced while in space).
Apparently, jellyfishes of the species Turritopsis nutricula are biologically immortal; although they can die of disease or being eaten, they are able to thwart dying of natural causes by periodically returning to the infant polyp stage. Theoretically, there could be T. nutricula in the oceans that have lived there since the beginnings of life on earth.
Five hats means that five tropers think it is ready to publish.
You are saying that you think this draft is ready to be published. That means the description is not ambiguous,
it doesn't duplicate an existing trope, there are at least three examples, and the title makes sense.
Is that what you meant to do?
You are saying this draft has a ready-to-publish hat it does not deserve and you are taking it back.