Becoming a Weapon Master, Starting as a Witcher

Hyperthymesia × Asperger's Syndrome × Obsessive-Compulsive Disorder.

Chosen by a god for his remarkable medical history, Chen Xu enters the battlefield of the gods' chosen. Blessed by divine power, his various conditions give rise to uncanny abilities that combine the strengths of the human brain and artificial intelligence:

A single swing of a scythe is enough for him to grasp the feat [Blade Mastery], attaining proficiency on par with a master who has devoted decades to the blade. Crouching down to tie his shoelaces grants him the skill [Stealth], transforming him into a deadly shadow between light and darkness.

Whatever the technique or discipline, he reaches elite proficiency the moment he tries it. One second, you are his teacher; the next, the student need no longer be inferior to the master.

Starting in The Witcher 3, he battles prodigies across worlds and faces crises of rogue machines, until the gods themselves enter the fray and he reaches the ends of all worlds. Note: This is not a mindless power fantasy. Most enemies are high-difficulty elites. If that isn't your thing, please pass.