I think that the fundamental conflict that George faces when he kills Lennie is the test of loyalty and betrayal. On one hand, he has been with Lennie for so long and supported him through so much that George feels loyalty towards Lennie. This is challenged at the moment that he must kill him. It is for this reason that George's hand wavers and there is some level of fear and reticence within him. This conflict is something that haunts at him when Slim steadies him by the arm telling him that what had to be done is what was done. It is here where George's conflict between loyalty to Lennie and his actions is most evident. What makes George's predicament all the more challenging is that his killing of Lennie is representative of George's love for Lennie. This is what makes his conflict all the more challenging in that he must kill that whom he loves. Throughout the novel George and Lennie had been inseparable. This bond is what causes the conflict within George for he recognizes that he must protect Lennie in this instance by killing him. This is where his conflict lies and where his struggle is most evident.