The user can achieve a superior form in between the "base" and "complete" levels. By certain standards, an evolution may require certain perquisites (such as time, amount ingested) to be met before the user can achieve the new form, and cannot be reached if anything is missing or removed (resulting in a failure that may cause either regression or even death). This ability allows the user to reach an evolved state without all the necessary steps in place, although with certain drawbacks.
After taking the Titan Serum, Rod Reiss (Attack on Titan) became a Titan, but as he orally ingested it rather than injecting it, he became a malformed beast, too large to even move properly.
Papillon (Buso Renkin) was forced to use an incomplete embryo to transform into a humanoid homunculus to counter Jiro's attempted sabotage, thus he did not acquire the emblem nor could he remove the pangs of his illness. However, he compensates this by combining his intellect and unbreakable will with his new superhuman strengths and eternal life to overcome all odds.
Mafuga (Doraemon) is a wind demon dragon formed from three wind spirits: Fuuko, Gorado, and a the Red Egg. Even after Fuuko was freed from the body, Gorado and the Red Egg recombined to form a less powerful Mafuga, though more evil since Fuuko's influence was absent.
Cell (Dragon Ball) in his incomplete form, in which his powers pales in comparison to his complete form, which requires the absorption of Artificial Humans #17 and #18 to achieve. He partially compensates this by devouring a large amount of human life energy, preparing him with enough power to overpower and capture the two.
Son Goku (Dragon Ball) was so enraged at Lord Slug that he took on a Pseudo Super Saiyan state against him. While not a true Super Saiyan form, Goku nonetheless gained enough power from the state to easily overpower Slug, when he was no match for him before.
Gaara (Naruto) was forced into an incomplete transformation into Shukaku due to being injured by Sasuke's Chidori in between his phase. As a result of his mental instability of seeing his own blood, he could not focus on taking the form of the tailed beast within him, and was severely hampered compared to if he had the time to fully transform.
Mizuki (Naruto) used an incomplete experimental potion from Orochimaru to achieve an animal-hybrid transformation, which gave him an explosive burst of powers. However, because of this incomplete formula, Mizuki eventually suffered from a cellular destruction backlash that would have killed him had Tsunade not saved him; he nevertheless lost all of his ninja capacities.
The Ten-Tails (Naruto) was revived uin an incomplete form due to Obito losing his patience in capturing Gyūki and Kurama, thus resulting in a severely weakened form (by comparison), though by no means was it any less threatening to the world. Nevertheless, Black Zetsu did not want this form to revive Kaguya, as it would result in her being severely weakened.
Obito Uchiha (Naruto) becoming the jinchūriki to an incomplete Ten-Tails, thus his form is also incomplete. However, he still became the strongest being at the time of his transformation, with sufficient power to subjugate the entire world. He did not possess the full powers of the Rinnegan, thus Black Zetsu did not want to use him as the vessel for Kaguya.
Bob (ReBoot) merged with his keytool, Glitch, when it was damaged, thus resulting in a form that can be considered a failure. Continuous usage of his Glitch powers would risk total fragmentation, and separating was a very risky move that nearly cost him his life.
HAOS (Resident Evil 6) was awakened before it was fully completed, leaving it in an incomplete, though still deadly and powerful form.
Alf Layla wa-Layla (Sonic the Hedgehog) is the form the Erazor Djinn takes after absorbing the World Rings and killing Shahra the Ring Genie; however, as Sonic, the one who collected the World Rings, was not sacrificed, Erazor did not gain full control over the rings, resulting in his transformation being incomplete, though no less threatening to the world.
Dark Gaia (Sonic the Hedgehog) was awakened in an incomplete state when it was prematurely awakened by Dr. Eggman, though it was no less threatening to the planet.
Using four Chaos Emeralds, Turbo Mecha Sonic (Super Mario Bros. Z) enters a "semi-super" state. While not his true super form, Mecha Sonic was powerful enough to easily trounce the Axem Rangers X and Mario's team all at once, and generate an energy ball powerful enough to utterly annihilate Yoshi's Island.
After suffering a brutal beating at the hands of Splinter, the Shredder (Teenage Mutant Ninja Turtles 2012) underwent a mutagen treatment to become the powerful Super Shredder. While incredibly powerful, the mutagen formula he used was unstable, causing side-effects such as his arm to painfully shrivel up.
By repeatedly cannibalizing other Ghouls, Ken Kaneki (Tokyo Ghoul) eventually mutated into a Kakuja, developing a secondary kagune that serves as natural armor and enhances his strength. However, Kaneki's Kakuja transformation is currently incomplete, resulting in him losing his sanity and becoming a psychotic berserker.