I don't think Conan, as written by REH, progresses through D&D-type levels or "build".
In
The Tower of the Elephant he kills a lion with a single sword blow:
It was Conan's savage instinct which made him wheel suddenly; for the death that was upon them made no sound. A fleeting glimpse showed the Cimmerian the giant tawny shape, rearing upright against the stars, towering over him for the death- stroke. No civilized man could have moved half so quickly as the barbarian moved. His sword flashed frostily in the starlight with every ounce of desperate nerve and thew behind it, and man and beast went down together.
Cursing incoherently beneath his breath, Taurus bent above the mass, and saw his companion's limbs move as he strove to drag himself from under the great weight that lay limply upon him. A glance showed the startled Nemedian that the lion was dead, its slanting skull split in half. He laid hold of the carcass, and by his aid, Conan thrust it aside and clambered up, still gripping his dripping sword.
'Are you hurt, man?' gasped Taurus, still bewildered by the stunning swiftness of that touch-and-go episode.
'No, by Crom!' answered the barbarian. 'But that was as close a call as I've had in a life noways tame. Why did not the cursed beast roar as he charged?'
Conan is as puissant and mightily thewed as REH wants him to be! Which is
very much in both respects.