MTL - This Game is Not Easy - ~ Pseudo four

As a promise, he went out into the world as an assassin. 3 years later, after becoming the Supreme Assassin, he gave up on everything he had and returned to the ranks of ordinary people. But one day, Kismet, a mystical game created by the National Research and Development had appeared.

Enigmatic hands, spectral frame, and one cunning strike just like the swing of the Grim Reaper. The Supreme Assassin takes on the mystical world, and how his legendary tales sets off, progressively ascending the altar to becoming the best.

- Description from Novelupdates

God plucked one of his creations from his first Earth and gave him a second chance in another one of his Earths...surprise it is in DxD! Now reincarnated as a perverted side character how will our poor protagonist handle his new identity? Well he probably wont make the choices you will want him to, that's for sure!

I was a failed experiment

The human race fell under the wrath of the alien invaders. At the end, Michael, humanity's last Paragon, remained.Unwilling to let his kin be exterminated, he goes back in time to the year 4026. One week before the start of the alien invasion that marked the turning point in the war.Reborn in his young body with his memories intact, Michael will use the knowledge of his past life to his advantage.By mastering both cultivation and cybernetics, he will attain the power to protect his loved ones, with his ultimate goal being to raise humanity to galactic supremacy and triumph over the alien invaders once and for all!