Question

Which line from "Lather and Nothing Else." best reveals internal conflict?

Answer 1

A conflict is a decision you are having trouble making. Internal conflict is a conflict that you are having with yourself, internally- or in your head. 

"And it would be so easy to kill him. He deserves it. Or does he? No!"
Would be your answer, in this case.

Answer 2

Internal conflict refers to the state of mind which results in a struggle of opposing impulses and demands.

The line from "Lather and Nothing Else." by Donald A. Yates, that best reveals internal conflict is “And it would be so easy to kill him. He deserves it. Or does he? No!”.

This internal conflict arises within the barber of if he should murder Captain Torres. Though he knew the wrongs of the captain about murdering many people, yet he cannot let himself cross the moral line that in professionalism he should just cut the captain's beard.  Therefore, after much moral dilemma, he decides to not kill him and perform his duty.