With the aid of the Kaioken, Goku (Dragon Ball series) is able to increase his Ki reserves up to 20 times their natural limit, but at the cost of exhausting his body.
Whenever Master Roshi (Dragon Ball series) enters his MAX Power form, he gains a massive increase in power and muscle mass, allowing him to hold his own against strong opponents.
Beerus (Dragon Ball series) in his Angered State.
After becoming Super Saiyan Gods and adapting to its power, Goku and Vegeta (Dragon Ball series) became Saiyans beyond God, enabling them to use the Super Saiyan God power in their base forms.
After having all of his latent power unlocked by the Old Kai, Gohan (Dragon Ball series) obtained the Potential Unleashed form, his most powerful state of being.
The Future Warrior (Dragon Ball Xenoverse) is capable of utilizing both the Kaioken...
...and the Potential Unleashed form.
Using Namekian Fusion to merge with fellow Namekians Nail and Kami, Piccolo (Dragon Ball series) became a Super Namek, possessing power surpassing that of an untrained Super Saiyan.
Dabura (Dragon Ball series) uses Demonic Will to enter a powered-up state during his fight with Gohan.
Using Focus Spirit, Link (Hyrule Warriors) enters an enhanced state that increases his strength, speed, and defense.
Unable to wield armor like X, Zero (Mega Man X series) is able to posses the Black Zero enhancement, granting him an increase in attack powers, speed, and weapon energy.
Using the PED Suit and Phazon in her body, Samus Aran (Metroid) enters Hypermode, receiving a vast increase in firepower and strength.
When Liu Kang (Mortal Kombat: Shoalin Monks) executes his Brutality: Rage Mode, he enters a powered up state in which he covers himself in flames and becomes able to project powerful fireballs and pummel his opponents with fists of flames.
When Kung Lao (Mortal Kombat: Shoalin Monks) executes his Brutality: Razor's Edge, he enters a powered up state in which his Razor-Rimmed Hat becomes a deadly weapon in his hands, slashing his enemies multiple times before decapitating them.
Users of the Eight Inner Gates such as Rock Lee, (Naruto) are able to open them in order to gain access to a great amounts of chakra at the cost of doing extreme damage to their body.
When he possessed the Cursed Seal of Heaven, Sasuke (Naruto) received an increase in chakra and physical abilities. At the seals' second level, he was able to fight on par with Naruto's One-Tailed form.
By using Gear Second to increase the flow of blood throughout his body, Monkey D. Luffy (One Piece) enters a state in which his strength and speed are greatly enhanced.
By releasing her limiter, Aigis (Persona 3) enters Orgia Mode, her most powerful state of being.
The Lost Galaxy Rangers (Power Rangers Lost Galaxy) can use the Lights of Orion to access a state in which they able to enhance the strength of most their arsenal and ultize their Power-Up Mode.
The Lost Galaxy Rangers can also use the Lights of Orion to empower their Galaxy Megazord and its saber.
Using Dark Gaia's power, Sonic the Werehog (Sonic Unleashed) enters Unleashed Mode, gaining enhanced strength, speed, and durability.
Whenever Shadow (Sonic the Hedgehog series) removes his Inhibitor Rings, he becomes Chaos Shadow, allowing him to tap into a limitless supply of Chaos Energy while draining his stamina.
Even with his Inhibitor Rings on, Shadow (Sonic the Hedgehog series) can enter an enhanced state of being via Chaos Boost.
When Chase Young (Xiaolin Showdown) transforms into his lizard form he becomes much faster and stronger.
Tsukune Aono (Rosario + Vampire) enhances his strength by releasing the first seal of his Holy Lock.
Those infected with the Hercules virus (Punch Line) can Uberfy, causing them to gain superhuman strength and speed.