The ability to merge separate powers into a single whole and combine/merge powers to create combos or even to create a new force. Sub-power of Superpower Manipulation. Superpower variation of Amalgamation.
The user can merge two or more powers to create new powers as well as different combinations. Sometimes the second ability may be naturally born, on others it may have been taken from another by force.
The users can even use two or more separate powers simultaneously to use for various uses.
Due to his hybrid nature, Ichigo Kurosaki (Bleach) can combine the unique powers of Hollows, Quincy, and Shinigami...
...Which is apparent with his dual bladed Zanpakutō, they of which contain separate powers: with the left blade, which is the smaller one, contains his Quincy powers, and the right blade, which is the larger one, contains his Shinigami & Hollow powers.
Due to having assimilated Kaien Shiba, Aaroniero Arruruerie (Bleach) can use Kaien's Shinigami powers on top of his own Hollow powers.
As an artificial hybrid meant to mimic what Ichigo naturally was, Hikone Ubuginu (Bleach) can also combine the various unique powers of Hollows, Quincy, and Shinigami to maximize their power and efficiency.
Clow Reed (Cardcaptor Sakura) combined both Eastern and Western magic to create the Clow Cards.
The One Being Sought (Code: Breaker) was born with the two abilities "Absolute Space" and "Cell Regeneration", granting him a powerful offense and defense.
Shigure (Code: Breaker) can manipulate "Ash" and use the "Giga Phantom" to increase his body parts size.
Hachiouji Saechika (Code: Breaker) can manipulate "Shadow" and "Effacement" to induce death around him.
Sasuke Uchiha (Naruto) transplanted his brother, Itachi's eyes into himself combining both of their individual Mangekyō Sharingan into a single and more powerful version in the form of Eternal Mangekyō Sharingan…
One For All (My Hero Academia) is a quirk that can stockpile power for the user, granting them immense strength. "One For All" was originally two quirks merged into one, a quirk that grants strength and an unknown quirk that could be passed onto another.
All for One (My Hero Academia) is an ability theft based Quirk that allows its user to steal and stockpile countless Quirks, combining them in various different ways. Such as combining Muscle Coiling with Air Pressure and numerous attack power/strength augmentation abilities to magnify its destructive capacity.
Issei Hyodou (Highschool DxD) awaken the Diabolos Dragon Armour after combining the power of the Ouroboros Dragon and the Welsh Dragon into a single form.