My Reflector Is Invincible

The game “The Valentino Saga” is about taking down the Demon King.
The player has managed to complete 99.99% of the impossible achievements that everyone else had given up on.
The only one left is…

“Damn, 18 years? I have to watch the opening animation for 18 years?!”

When he opened his eyes, he found himself inside the game world, with the power said to be the strongest in the world.

[You have acquired the Demon King’s Unique Ability (Reflex)]

But in the worst possible way.

“Execute the criminal.”
“Kill that slave!”
“Die, you vermin!”

Not only was he possessed by the weakest character, but they wanted him dead the moment he arrived?

Not a chance.

“Rainbow Reflex! Damn you all!”