The last three lines of dialogue reaffirm the details we already know, or have at least inferred by now: Walter's extreme betrayal of Keyes, Keyes' hurt caused by this wrong, and the still undying love between the two. Walter had told Keyes he loved him sarcastically in the office one time before in his brusque macho staccato, but when Walter says "I love you too," he means it this time. The repetition of the same line, one a sarcastic barb and one an earnest admission, shows arguably the only growth on Walter's part as an individual, and it is still in fact characterized by his relationship with another.
The final action in the film takes place as Keyes lights one last cigarette for Walter, a visual motif used throughout the film. To Walter, it is as if a cigarette is a phallic symbol of male bravado. As he works through his plans with Phyllis, he constantly smokes and lights his cigarettes in a stylized, confident fashion. Lying on the floor, eviscerated of both his power over this woman and many of his red blood cells, he is figuratively and literally unable to assert his masculinity in his traditional style. Everything about this final frame's composition highlights the contrast in nature between Keyes and Walter. The former hovers physically over the latter, as if to say "well, I'm not bleeding to death." He is cool and collected, while Walter is panicky and sweating. Walter is even slightly closer to the camera, as if to show that Keyes, while an important part of Walter's life, is able to call himself somewhat removed from Walter's crime. He lights Walter's cigarette for him in a style similar to Walter's own (with the thumbnail), reaffirming Walter's emasculation yet also lovingly, emphasizing the importance of their eternal male