The MC was an existence the original world wanted to keep hidden and tucked under as many blankets as possible.
He was literally the Alpha and Omega of that world, able to either keep it in peace, or end it with just one thought.
That is why his powers are so OP, just one command and he can literally kill anything. Oh did i mention he can even kill death, so he is essentially immortal.
This is why when he suddenly disappeared from that world, they literally had a party to end all parties.