The Ending (Situational Irony)
Of course, the most infamous instance of irony in Taxi Driver are the scenes that follow the climactic bloodbath. One of Travis' defining characteristics is his alienation from society: no matter what he does, he cannot reconcile with the world at large. Everything and everyone disgusts him, and in turn, nothing seems to go his way, and people reject him. But now, having recklessly attempted to assassinate a presidential candidate, getting chased by members of the Secret Service, then gruesomely killing three people in a brothel, Travis receives accolades from the press and effusive thanks from Iris's family. Furthermore, when he coincidentally picks up Betsy in his cab, she is no longer cold towards him, and seems to admire him for his recent violent acts. Just when we expect Travis to have fully cemented his position of total alienation from society, the world embraces him with open arms. The ironic distance between the crazed gun-toting vigilante assassin we have known and the public's perception of Travis as an angel of redemption is a huge source of irony at the end of the film.
War Hero Turned Vigilante (Situational Irony)
Travis's status as hero in the urban war between good and evil is also ironic because hitherto, he was an unsung veteran of an actual war. Travis is a Vietnam War veteran, a loyal and disciplined marine. History tells us that many vets returning home from the war in Vietnam did not receive a hero’s welcome, and were reviled and looked down on for participating in an unpopular war. Travis is a quintessential example of the overlooked Vietnam veteran, tossed brutally back into a domestic life where people had little respect for his service.
The irony lies in the fact that it is not until Travis commits his anarchic violence against the pimps and johns of New York, having lost his faith in the government under which he served, that he receives a proper hero's thank you. The world is more prone to valorize Travis when he goes outside the law than when he serves in the military.
Betsy's Eventual Admiration of Travis (Situational Irony)
Betsy rejects Travis because he just doesn’t seem to understand how to behave within normal dating conventions, taking her to a porn movie. She rejects him on the basis of his ignorance to how to behave correctly. However, when Travis really eschews social conventions and commits acts of extreme violence, Betsy changes her tune.
Once society confers acceptance on Travis, she deems him worthy of her affection. The irony is that Betsy's principles are not as strong as her investment in Travis's reputation, once he is valorized by the press. A further layer of irony occurs when Travis drives away from her watchful eye contact, at the very end of the film. While Travis was obsessed with Betsy—indeed, it is what incited his entire transformation, and his "heroic" acts themselves—once he finally receives her attention, he doesn't want it anymore.
Travis's Heeding Palantine's Words (Situational Irony)
After Betsy rejects him, Travis becomes obsessed not only with her, but with the candidate for whom she works. He attends rallies, with an enigmatic and menacing smirk, and plasters headlines about Palantine on his wall. The viewer cannot tell if Travis loves and identifies with Palantine, or is filled with menace and vitriol. Indeed, we soon realize that his devotion is nefarious: Palantine has become the punching bag for Travis's feelings of isolation and rejection, by Betsy and the world at large.
The irony of Travis's feelings towards Palantine comes when he watches Palantine make a speech on television. Palantine urges citizens to "rise up" and take control of the country in the way that they want to. Travis uses these urgings for independent action and uprising as justification and motor for his own vigilantism. From Travis's warped perspective, Palantine's encouragement to "rise up" is an encouragement to carry arms, commit violent action—and even attempt to assassinate Palantine.
Travis's Racism & Lack of Self Awareness (Situational Irony)
One of Travis's greatest flaws is his lack of self-awareness. This comes out most pointedly in his persistent racism throughout the movie. It is glaringly obvious that Travis equates black men with threat. He has no problem at all pulling out his weapon and using it against a black robber inside the convenience store, at the diner with the other cabbies he looks at the black men surrounding them suspiciously, and he even treats fellow cabbie Charlie T. with paranoia and fear. The irony is that while Travis is most suspicious of the black people in his orbit, his racism blinds him to the fact that some of the most violent people in his orbit are white, and themselves violently motivated by racism—e.g. the man he picks up who wants to kill his wife, who is cheating on him with a black man.
