The question's tricky because there's no single book with that exact title—it’s more of a popular trope name in webnovel circles, especially for Chinese xianxia or Korean fantasy reincarnation stories. Usually, the 'supreme reincarnated' setup involves a legendary cultivator, immortal emperor, or ultra-powerful being who dies and wakes up in the body of a weak, despised youngster in a lower realm. The main plot follows them using their past-life knowledge and techniques to climb back to the top, uncover the mysteries behind their death, and settle old scores.
These stories often have a very satisfying power-fantasy core: watching the MC effortlessly crush arrogant young masters, invent overpowered cultivation methods, and collect loyal allies (and love interests) is a big part of the appeal. The central tension usually comes from a hidden enemy from their past life, or a larger conspiracy threatening the world they now have to protect. Honestly, after reading a few, the plots can feel pretty similar—but the execution of the revenge arcs and the world-building details are what make or break a specific novel.