Guan Yu killed Pound with integrity, why not kill Yujin without integrity?

This is because Guan Yu despises the ban very much. He thought killing him was an insult to himself. Moreover, Guan Yu thinks that killing Pound, who has integrity, is more respectful to him. Because Pang Tailin is not strong enough to die, if he is forced to surrender, he will do great harm to himself. Once people like Yu Jin surrender, they will even rebel. Perhaps this will disturb his morale, so he might as well not kill Yu Ban, and it can also be used as a bargaining chip with Cao Wei.

Of course, we know that Guan Yu was defeated and Yu Jin was saved. But later, many people looked down on Yu Jin, because Yu Jin surrendered to Guan Yu at that time and failed to keep good faith. And later, when Cao Pi was in power, he was repeatedly humiliated by the ban. Finally, it led to suicide. So people like Yu Jin were looked down upon by many people at that time. Although he was also a great star, he didn't keep his integrity in his later years.

People like Pound chose to kill Pound because they were recognized by Guan Yu and others. Because if Pound is not killed, he will definitely make a comeback, which will do great harm to himself. So at that time, Guan Yu chose to kill Pound in order to put an end to such harm. At that time, Pound was killed as a general of Cao Wei, which would make the morale of Cao Wei Group turbulent.

So it is reasonable that Guan Yu chose to kill Pound instead of hurting him today, but what happened later was not as simple as Guan Yu imagined. Instead, Guan Yu was defeated and killed, while Yu Jin survived. Of course, it didn't end well in the end