The Sky-Splitting Bolt was Liam's true killing blow. It couldn't reach the Seven Hellish Steps' max power, but its range and piercing properties made it a far safer and viable tool.
Of course, there were flaws. Perfect attacks didn't exist in the world. In the Sky-Splitting Bolt's case, its size and casting time were weaknesses that had become more relevant as the quality of Liam's opponents increased.
Branching experts wouldn't give Liam the time to cast the weapon art. Taking them by surprise also wasn't always feasible since their superior stage awarded them with greater perception and survival instincts.
Those powerful cultivators wouldn't even die easily. Blowing up their heads seemed to do the trick, but that was the hardest spot to hit when it came to a moving target.
Also, that wouldn't work forever. Liam had seen as much with Crazy Uncle.
