Infinite Dragon Beast: Taming Ice Dragons with SSS Ranked Talent - Chapter 21: Aurora Magic Power

A child was born unable to cultivate Inner Strength. In order to gain his father's attention and regard, he resolutely chose the painful and difficult path of cultivating Outer Strength. As spring gave way to autumn, time flew by, and the child grew up... he became a young man. What truly changed his destiny was a mysterious Crystal Stone formed from a meteor—the Meteor Tear. This Meteor Tear, unbeknownst to the young man, merged into his body, and like a caterpillar transforming into a butterfly, the young man metamorphosed... And with that transformation, everything changed. And his father finally came to realize the astonishing strength of the son he had never truly invested his Heart Power in...

In regards to the MMORPG Cross Reverie, Sakamoto Takuma boasted an overwhelming strength that was enough for him to be called the Demon King by the other players. One day, he gets summoned to another world with his appearance in the game. There, there are two people that insist “I am the real summon master.” Takuma gets slave-turning magic used for summoned beasts cast on him by the girls –

You thought being reincarnated as an extra-side character was bad? Imagine being thrown into the body of a villain who is disowned by his own family and discarded by the author.