what is a quote that illustrates why Frenchie did what he did in chapter 15. Do you agree with his actions?

Do you mean when Frenchie shoots Travis? I'm not sure we can completely judge Frenchie here. Ri Ri is dead and Frenchie understandibly loses composure. Here for the first time is an enemy at his mercy. Ri Ri never had a chance; Frenchie doesn't want to give this guy a chance.