Perseverance
"But you're a Martial Squire." Rui frowned.
"I held back to match your physical power." He shrugged. "As long as you master it perfectly, the result shouldn't deviate much from this."
Rui was quite excited at the prospect of obtaining that kind of lethality, that he resumed the torture training immediately. This time, he even stopped screaming. Bearing the pain and putting his toe through utter hell with each kick.
A little over an hour passed, and he had just completed a thousand kicks!
He glanced at his toe, after he healed it for the tenth time. It didn't look any different at all. But, that obviously to be expected, if the process would be completed over the span of a million kicks, then there would be no visible progress over merely just a thousand kicks, which was 0.1% of the total progress.