Okay, so we have 2 people person A and person B
Person A has a weapon and wants to kill B, but then a new Person who we call "C" shows up to convice person to not do it because killing is bad or whatever.
That is not the main problem until what usually happens later which is them just dropping the weapon on the ground like idiots.
Now because Person B has a higher IQ than the age of a Libetarians dream partner, they do the most predictable thing in the entire world ans grab the weapon for themselves. Ans threatnes the other 2
Also the trope of the protagonist slaughtering dozens on unnamed goons only to spare the main villain because, "killing is bad".