The user can transform their bodies or weapons into their true forms if sealed, restrained, or just not activated, unlocking their dormant power in order to drastically increase their regular power. All their original abilities are increased along with gaining new abilities to their full power.
The Archfiend Vazdah (Ninja Gaiden II) in his true form.
Edrad Liones's (Bleach) true form Volcanica.
The true form of the two Zangetsus.
Komamura and Kokujō Tengen Myō'ō: Dangai Jōe's true forms.
Orochimaru's (Naruto) true form.
Frieza (Dragon Ball Z) in his true form.
Kid Buu (Dragon Ball Z) is a Pure Majin, the true form of Majin Buu.
Link's Master Sword (Legend of Zelda) in it's true form after being blessed by Hylia's mortal form, Zelda.
Whenever Ryu Hayabusa (Ninja Gaiden series) places the Eye of the Dragon into his Dragon Sword, it becomes the True Dragon sword. In this state, the blade brims with the power of the 12 Divine Dragons and becomes a weapons of immense power.
Sora (Kingdom Hearts) in his final Drive form.
Sol Badguy (Guilty Gear) in his true form, Dragon Install.
Chakravartin (Asura's Wrath) in his final form.
Envy (Fullmetal Alchemist) has two true forms: the monstrous reptilian form when empowered by the souls of the population of Xerxes (above), and the helpless little lizard form when most of his core is damaged (below).
Chase Young (Xiaolin Showdown) in his true lizard form.
White Raven is Raven's (DC Comics) most primal, significant, and powerful version, mostly shown as a symbol of her highest hidden power and her inner purity against the consuming evil of her father
Marluxia's (Kingdom Hearts) final form.
The Master Core (SSB4) in it's true form after being defeated in it's other forms.
The Master Core (SSB4) is the true form of Master Hand.
Rushu (Wakfu) in his true form.
Shadow the Hedgehog (Sonic the Hedghog)
Krishna (Hindu Mythology) revealing Vishvarupa/God-Form, to Arjuna who's unable to bear it (Baghavad Gita)
Lille Barro (Bleach) is able to enter his true form upon decapitation.
Kamen Rider Kiva (Emperor Form)
Like must others Etherious Demons, Mard Geer (Fairy Tail) is able to transform into his true Etherious Form.
Jackal's Etherious Form (Fairy Tail)
Doriate's Etherious Form (Fairy Tail)
Franmalth's Etherious Form (Fairy Tail)
Ezel's Etherious Form (Fairy Tail) Slash Attack Mode.
Kyouka's (Fairy Tail) Etherious Form.
Torafusa's (Fairy Tail) Etherious Form.
Tempesta's (Fairy Tail) Etherious Form.
Hoopa (Pokemon) in his true unbound form.
Zygarde (Pokemon) in his true form with 100% of his cells.
After reabsorbing the final fragment of its essence from Sonic, Dark Gaia (Sonic Unleashed) was able to fully mature and reassume its true form, Perfect Dark Gaia.
When granted access to Six Paths Chakra by the Sage of Six Paths, Naruto Uzumaki (Naruto) can access a transcended version of his trademark Sage Mode...
...and access an even greater version of the Six Paths Sage Mode when he mixes his Sage Chakra with the Chakra he draws in from the Nine Bijuu's