Wo Kaiju Shenhua Tianfu, Yi Jian Zhan Shen!

Su Ming was once the world’s number one assassin, a hero who saved billions of his fellow humans and was honored as one of the Ten Great Powerhouses of the Dragon Nation. Yet, he was betrayed by the woman he loved and the brother he trusted, dying with hatred in his heart and buried within the S-class dungeon known as the Death Cavern. Unexpectedly, he is reborn, returned to his high school days, on the very day of the awakening ceremony. This time, he gains a myth-grade talent upon awakening! (Source: Kuaikan, translated)