Maybe it's to create a sense of mystery or leave room for the reader's imagination.
In a more literary sense, if a story contains a segment where a character is being roasted (perhaps verbally attacked or made fun of in a comical way), 'cut off the end of the roast story' could imply that the author or storyteller decides to end this particular aspect of the plot earlier than expected. This could be for various reasons such as pacing the story better, not wanting to overemphasize the negative or comical aspect too much, or simply to move on to a different part of the story more quickly.
It could mean trimming the unwanted parts at the ends of a story about a roast. Maybe it refers to removing the less relevant or uninteresting beginnings and endings of a narrative related to a roast, like a roast dinner or a roasted item.
If it's a written story, you simply delete the initial paragraphs that are not crucial to the main plot and the final paragraphs that seem like unnecessary add - ons.
One reason could be time. If you're in a situation where you don't have much time to tell the whole story, you might cut off the end of the roast story. For example, if you're chatting during a short break.
You can avoid cutting off the end when cooking roast beef. Start by choosing a good-quality piece of beef. Marinate it if you like. During cooking, keep an eye on it to ensure it doesn't overcook and you'll have a delicious roast without any end cutting.
Maybe it's because of the damage or deterioration of the original manuscripts over time.
Since there's no more context about this 'cut off big toe with axe story', it's impossible to say who did such a thing. It could be anyone in the story's context, but without further details, we can't determine it.
The reason Chen Pingping was eventually executed by a thousand cuts was because he had attempted to murder the Qing Emperor and his sons. During the Qing Emperor's investigation, he discovered Chen Pingping's plot and recalled him. In the Qing Emperor's royal study, Chen Pingping used the shotgun on his wheelchair to heavily injure the Qing Emperor. As punishment, Chen Pingping was sentenced to death by a thousand cuts. Before he died, Chen Pingping asked Fan Xian what was in the box Ye Qingmei had left behind. Fan Xian told him it was a sniper rifle. Fan Xian's answer showed that Chen Pingping was trying to avenge Ye Qingmei. As a result, Chen Pingping was eventually executed by the Qing Emperor.
The reason Xu Fengnian cut off Zhen Wu was to get rid of the burden of his previous identity. He chose to cut off the connection with his previous life and lost the ability to use Zhenwu Great Emperor's power, but he also got rid of the shackles of his previous life's identity. This allowed Xu Fengnian to pursue his own goals with his own strength and was no longer controlled by the immortals in the sky. He didn't mention the specific reason for his decision.
The Joker cutting his face off is a symbolic act of completely letting go of any pretense of normalcy and embracing his insanity to the fullest. It's a shock tactic to terrorize and confuse his enemies.