Some time ago, Dana suggested a parallel between Hamlet-Claudius and Blake-Travis dynamics.
When asked why Hamlet refrains from killing his uncle, I usually resort to the explanation Nietzsche gave in 'The Birth of Tragedy'. Nietzsche compares Hamlet to 'Dionysian' heroes who do not act because they have realized the complexity of the world, seen beyond the idealistic half which the culture normally perceives. Initially Hamlet is a 'happy prince' within a perfectly functioning patriarchal structure. His father, likened to Jove, Apollo, Hercules, is the epitome of all the virtues valued by this structure; his mother likewise performs dutifully all functions assigned to her within the structure. Then Claudius, likened to Satire, bursts upon the scene. Hamlet has to deal with much more than just a single villainy committed by a single villain - he has to deal with his own realization that there are human actions prompted by dark, instinctive urges beyond rational control. Women are especially 'dangerous' and unreliable in this respect: Hamlet is shocked by the fact that his mother can have fun indiscriminately with Apollos and Satires alike. To conclude, Hamlet delays his revenge because his world has been irrevocably changed and he knows that killing one man won't restore his lost innocence or bring back his 'paradise lost'. Finally he decides to act because he accepts it is his human duty, a part of his destiny. 'Readiness is all.'
With Blake, the situation is somewhat different. I don't think he's ever had any illusions regarding the Federation (except while he was brainwashed) or the Universe he lives in, but he may have had some regarding his own soul. Blake has lost the 'innocence' of his soul after his capture and the death of his family and friends - when his initial, altruistic and rather abstract motives for fighting against the Federation were joined by other, private and not so impeccable ones. Blake is not a completely 'healthy' hero fighting an evil opponent: all the while he has to grapple with his own dark urges, most of all with his desire to indulge in personal revenge.
Like Hamlet, Blake knows that killing one villain won't change or annihilate this deeply disturbing experience of the self, help him get rid of the 'Travis' part of his own psyche. Hamlet is shocked by his revelation that the world is an unweeded garden; Blake is, I think, more disturbed by discovering this garden within his own soul. Realizing they cannot go back to the original state of innocence, they both proceed to do what they consider their human duty.
Some more traditional interpretations of Hamlet also emphasize the religious aspect of his dilemma, the fact that the vengeance in Shakespeare's time was considered a deadly sin (since God said, 'Vengeance is mine'), and the avenger was condemned to Hell. Given that all sorts of religion were banned within the Federation, I wonder if Blake's refusal to kill Travis could also be related with some remnant of those forgotten teachings. We know that Blake was interested in history and it's possible that he also studied various ethical systems of the past, trying to establish the principles upon which post-Federation world might be organised. His own feeling of morality is often at odds with his age, and although I like to think it is innate, it may have been acquired by studying as well.
I agree with what Ellynne said about Avon's part in this matter. Avon can 'solve Blake's problem for him', as he says in the Keeper, unlike Blake, he can kill Travis in a cold and impersonal manner ('I'm the one with brains and no heart', as he says to Travis in Star One). It's not until S3 and Shrinker that we get to see Avon dealing with the issue of personal revenge. His animosity towards Servalan, I suppose, also becomes more personal after he gets the Terminal disease.
N.