A guy struggles with everything and every day he is so close to dying some would mistake him for a corpse. But he survives. Every time he is nearly killed he slips away. He is well known, but not important enough to try and catch him.
After years of pain, several captures, enslavements, etc. the mc finally achieved something. He slipped away so many times he eventually perfected his technique. He was so experienced in surviving even the toughest environments and tricking death, he got another form of power.
He wasn't a mage, nor an assassin or warrior. The only thing he had was experience of countless battles. More than even the mighties king had. At the age of 47 he finally achieved something that was normally achieved at the age of 3.