Slowly Slipping Into Evil: He tries to convince himself that all of his actions are in the right, without letting himself become aware of his increasing violence and irrationality. See the entries under Villain Protagonist below.
The Atoner: In one ending, where he chooses not to cross the line and decides to be punished by law.
Much of the game could be interpreted as him trying to atone for the "white phosphorous incident", but his being hopelessly misguided only succeeds in making things worse.
Believing Their Own Lies: He swiftly abandons their actual reasons for being in Dubai in favor of stopping Konrad, so he can be a hero.
Blood Knight: Horribly, horribly deconstructed. If he weren't so obsessed with Konrad, maybe he would have realized that he was breaking down. Although, considering the obsession came from his delusions and his inner desire to project his guilt on someone else, this trope is more of a consequence than a cause.
Bolivian Army Ending: In the epilogue, Walker can either choose to lay down his gun to the U.S reinforcements or to fire upon them, thus invoking a last stand. Even in the event Walker survives the fight, other reinforcements will eventually come - and Walker greets them the way he did his own men to ensure the reinforcements will pursue him. "Gentlemen, welcome to Dubai."
Break the Badass/Break the Haughty: Over the course of the game, his confidence that he will be able to help save the day erodes. This is seen in his rage at the situation, which increases constantly.
Dead All Along: Of the Dying Dream variety. The developer states that one possible interpretation of the game is that Walker died in the helicopter crash in the beginning of the game and everything that came after was either his dying hallucination or his personal purgatory.
Death Seeker: In several of the game's endings he has effectively become this (the only one in which he's not is the one in which he kills himself). This aspect of his character may explain why, for example, he instructs Adams to fly the helicopter straight into the sandstorm.
Determinator: Brutally deconstructed. One of the rare cases in fiction where determination, and the resolve to continue your mission, doesn't make everything alright in the end. Sometimes when people tell you to stop, it would have been better if you'd listened.
A Father to His Men: Word of God says Walker's characterization at the beginning of the game is meant to evoke this trope. And only at the beginning of the game.
Foreshadowing: During one of his hallucinations, Walker sees Lugo begging for help, while a sea of civilian corpses drag him beneath the sand. Not long afterwards, Lugo is murdered by an angry mob of civilians. You can complete the foreshadowing, if you choose to listen to Adams and murder the mob in retaliation afterwards.
Good Scars, Evil Scars: Collects a number of disfiguring scars over the course of the game, mostly to his head.
The Hero: Tries to be one. And boy, you can stress that word plenty, especially after he crosses the point of no return.
Heroic BSOD: He goes through one when he finally realizes what he became after seeing Konrad's corpse. Although, at this point, it's hard to tell if this trope applies or if we're witnessing a Villainous Breakdown.
It's then up to the player to choose how Walker reacts to this: will he be Driven to Suicide? Is he going to give into his delusions entirely? Or will he finally make a good choice and try to Atone?. According to Steam's achievements, it's the last solution that is preferred.
Heroic Wannabe: Part of what drove him to the extremes he takes in the first place is because of this persona. It does not end well, at all.
Konrad: You're no savior. Your talents lie elsewhere.
Glory Seeker: He is so focused on succeeding at his mission that he is willing to order his men to accompany him In Harm's Way. However, as the hallucinatory Konrad mockingly reminds him, there was never really any need for him to do so, since his mission was strictly to reconnoitre Dubai for signs of life, then report his findings. This also explains his motivation for perceiving Konrad as the villain of his mission; given his desire to be a great hero, he subconsciously believed that he must attain that desire at the expense of the greatest hero he ever knew.
I Did What I Had to Do: This is his excuse for all the things he does in order to take down the 33rd. It becomes increasingly clear that he's just deluding himself.
Icy Blue Eyes: They're his most noticeable physical feature. Near the end of the game, after Walker has reached the conclusion of his character arc, they become especially haunting — hollow and dead. Should Walker shoot Konrad's "ghost", then one of the U.S. soldiers sent to rescue him even comments, "Look at his eyes... He's shell-shocked."
Irony: Walker initially serves as the leader of a search team sent to find a famed infantry battalion stranded in a sand-flooded Dubai. In the epilogue, he is found by a rescue force after becoming stranded in a sand-flooded Dubai due to the deaths of Adams and Lugo.
Death by Irony: Possible. Walker fires on the members of said infantry battalion in self-defence, and later makes it his team's mission to kill the battalion's now-disgraced commanding officer. Should Walker, now the disgraced former leader and sole survivor of an elite Delta team, choose to fire on the rescue force in the epilogue, he can be killed in self-defence.
The Kirk: Played straight early on where he has to settle conflicts between Adams and Lugo. Later, as he becomes increasingly mentally unhinged, it becomes their turn to try to rein him in, but to no avail.
Knight Templar: Progressively over the course of the game. He is finally called out on his actions most explicitly in the endgame.
Large Ham: Martin Walker goes from being a composed, steely-nerved leader to a deranged psychotic who screams curses at any given opportunity after the Freak Out. Given the nature of the game, it's deeply disturbing rather than Narm-y.
Early Game Walker: Tango down! Mid Game Walker: Kill fucking confirmed! Late Game Walker:GOT THE FUCKER!
Made of Iron: Falling off a skyscraper knocks him out for a while, but he gets up and goes straight back to fighting. Even more telling is that despite the various injuries he suffers over the course of the story, he never complains or takes stock of them in any way.
Mercy Kill: Inflicts these in his executions and potentially against Riggs, who is trapped under the water truck. Later subverted; they become more brutal and sadistic, first after the white phosphorus mortar, then after the helicopter crash.
Military Maverick: Walker defies orders to scout out the situation and retreat in favor of going on to rescue McPherson and determine the condition of the 33rd. If only he'd stopped when he had the chance...
Never My Fault: He ostensibly throws blame for his own actions and their consequences anywhere but on himself, especiallythe white phosphorous incident. However, it becomes increasingly clear that he's simultaneously riddled with self-loathing because of what he's done, even as he denies his fault. The game makes some pointed remarks about cognitive dissonance.
Pinball Protagonist: Claims to be one of these, constantly asserting that everything he does is because the enemy is forcing his hand. In reality, he's anything but.
Redemption Quest: A very dark example, almost to the point of deconstruction. Walker's continuing efforts to intervene in Dubai and improve the situation are in part motivated by a subconscious desire to redeem himself after the white phosphorous incident. However, he only succeeds in making the situation even worse.
Sanity Slippage: Throughout the game after the white phosphorus incident, but especially toward the end.
Ax-Crazy: Progressively, he becomes a more violent person.
Black and White Insanity: Has shades of this as the game goes on, continually trying to convince himself that the events of the plot fit into a dichotomous moral framework in which he and Delta are the "heroes" and the CIA, Konrad and the 33rd are the "villains", and any crimes that Delta commit in the course of stopping them were committed because the "villains" forced their hands. This is intended as a commentary on conventional shooter games which employ Black and White Morality (whether explicitly or implicitly) and players which were expecting the game's moral framework to unfold as such.
Hallucinations: Both auditory (see Hearing Voices below) and visual, taking form whenever there is a white flash rather than a black one to signify a change in scene. They start becoming more obvious after the white phosphorous incident, but there are signs of it (several times there are several "fade to white" scenes, as well at least one billboard of Konrad, in the first chapter) before then.
Hearing Voices: Begins by hallucinating Konrad's voice after finding the white phosphorus-incinerated corpses of the Damned 33rd's officers, but it branches out into many other hallucinations over the course of the game, culminating in a hallucinatory Climax Boss in the form of Lugo.
Revenge by Proxy: If he listens to Adams; while some people in the crowd definitely murdered Lugo and the others at least failed to stop it, it's impossible for all of them to have been guilty or to know who the innocent or guilty are.
Send In The Search Team: He is the leader of a team meant to serve such a purpose at the beginning of the game. This makes the Irony in the epilogue wherein he alone is found by a similar search team all the more crushing.
Shell-Shocked Veteran: Along with the crushing blows to his mental well-being dealt throughout the game itself, his alluded-to experience in Kabul, Afghanistan (where he first met Konrad, who saved his life) was probably unpleasant — he never speaks about it any way but vaguely. Of course, Dubai only makes it worse. It'll even be lampshaded if he lives past the credits by the US soldiers who arrive to pick him up.
Shows Damage: An extensive case — he goes from clean, healthy and battle-ready to filthy, bloodied, scarred, and ragged. Comparing the character models from the beginning and end shows that he becomes all but unrecognizable.
Two-Faced: Gets a rather nasty burn on one side of his head from an explosion.
Sole Survivor: By the end of the game, he is the only military officer left in Dubai until the United States military comes to pick him up. Given the actions of the game, it is possible that he is the last person left alive in Dubai, period, unless the rescue forces survive.
Suicide by Cop: A possible ending, by the team of soldiers sent to pick him up and bring him home. Even in the event that Walker survives the initial fight, he has basically made himself a target for the remaining U.S military forces in Dubai. He knows he'll never leave.
Tautological Templar: In his Heroic Wannabe attempt to be badass, he ignores any clues that what he's doing is actually not the right thing, solely based on the idea that, since he is fighting Konrad, anything is justified. The problem is, he actually isn't fighting Konrad, and his actions led to far more devastation than existed before he arrived in Dubai in the first place.
Capt. Walker:(his thoughts as he dies) I said something about going home, and [Konrad]... you said, "Home? (scoff) We can't go home. There's a line men like us have to cross. If we're lucky, we do what's necessary, and then we die."
This is illustrated in the other choice as well:
U.S Sergeant: We drove through this whole city to find you, Captain. On our way here we...saw things. What was it like? How did you survive all this? Capt. Walker: Who says I did?
Lt. Alphonse Adams
Played By: Christopher Reid
Ace Pilot: Pilots a helicopter once during the story, a shown in an In Medias Res first part before Chapter 1, and again later in. "Ace" might not be the best term, however, as, if the Dying Dream is true for Walker over the entire game proper, the one time we see him fly, he ends up crashing fatally, at least by CaptainWalker's orders.
Captain Obvious: Sometimes, usually because he's shocked and trying to confirm what he really saw.
Death by Irony: Over the course of the game, he grows to question the mission tasked to Lugo and himself by Walker and prioritizes saving the lives of the civilians they were initially sent in to assess. He gets betrayed when those civilians lynch Lugo and wants revenge, then later, he dies in a Last Stand meant to allow Walker to escape and complete said mission.
Heroic Sacrifice: The "heroic" is debatable at that point in the game, but he holds off what remains of the Damned 33rd so that Walker can get to Konrad and finish him off. The tone of his parting words to Walker suggests that by this point, he may even have become a Death Seeker - simply so he won't have to live with what they've done in Dubai. The game never actually depicts the outcome of his Last Stand, but it is highly probable he was killed.
Semper Fi: At one point he says "Adapt and overcome, bitch." "Improvise, adapt and overcome" is a Marine Corps slogan, suggesting he served in the Corps prior to joining Delta.
Shell-Shocked Veteran: Gradually. Though it's less obvious than with Lugo or Walker, Adams' stoic, unflinching loyalty evolves into silent but complete disgust for the entire situation and the Delta squad's part in it.
Sour Supporter: Gradually transitions into this over the course of the game. After The Squad has committed a great amount of atrocities over the game, it's clear that the only reason he still listens to Walker is so he can justify his part in said atrocities as Just Following Orders. This is seen best when he outright blames Walker for Lugo's death and mimes firing a gun in Walker's face.
The McCoy: As the game progresses, and he sees how bad things really are in Dubai, he switches roles with Lugo, and prioritizes saving civilians over furthering any mission Walker tasks them with. Once those same civilians lynch Lugo, he returns to being The Spock, now disgustedly focused on just helping Walker finish the damned mission.
Revenge by Proxy: Exactly when you know he's really snapped after the mob lynches Lugo. While some were definitely guilty and the rest at least failed to stop it, you know not all of the could've done it and have no way to tell guilty from innocent.
Token Minority: The only named African-American character in the game. It's not done in a patronizing fashion, however, and he receives just as much Character Development as anyone else.
Vitriolic Best Buds: With Lugo. Though the "best buds" aspect becomes extremely strained as the game goes on, to the point where they come to blows and Walker has to shout them back to their senses. That said, when Lugo dies, Adams is very distraught, to the point of demanding to be allowed to kill the mob who killed Lugo.
Kill the Cutie: He is hanged by an angry mob of local ex-civilians before Adams and Walker can get to him.
Climax Boss: The hallucinatory one is, anyway, shortly before leaving Adams. He's a Heavy Trooper with far more health than a normal one.
Cunning Linguist: He is fluent in Farsi, Hindi, Turkish and Cantonese, all languages which would be extremely useful for a U.S. Spec Ops member to know. Granted, this is minus the "cunning", since the one time he tries to communicate with hostile forces in Farsi, Walker and Adams immediately feel This Is Gonna Suck, in part due to his attitude.
Deadpan Snarker: Pretty much the first thing you learn about him is that he cracks jokes constantly.
Walker: Lugo, do you even listen to the shit that comes out of your mouth? Lugo: No, sir. I believe it messes with my rhythm.
Death by Irony: Over the course of the game, he grows to prioritize the mission tasked to Adams and himself by Walker over saving the lives of the civilians they were initially sent in to assess. He is hanged by a lynch mob of those very same civilians.
Friendly Sniper: The sharp-shooter and generally the most emotive of the group.
Jack of All Trades: He is the group's radioman, general technical expert, medic, translator, and designated marksman. Comparatively, Adams just carries a larger gun and acts as the team's pilot.
Jade-Colored Glasses: After the white phosphorus incident, he started to grow more bitter and cynical.
The McCoy: Which leads to him being the most shaken of any of the squad.
The Spock: As the game progresses, and he sees the strain placed on Walker's decision-making abilities, he switches roles with Adams, and prioritizes any mission Walker tasks them with over the lives of the civilians they were initially sent in to find, even making what he feels are logical decisions without waiting for Walker's orders. He is then killed when those very same civilians turn into a mob and lynch him.
My God, What Have I Done?: After the carnage of the white phosphorus incident hits home, he starts screaming at Adams about how Walker turned them into killers.
Never My Fault: While not to the same extent as Walker, he ignores his own (albeit reluctant) role in the white phosphorous incident; his accusation that Walker turned him and Adams "into fucking killers" is especially ridiculous given that he's already killed scores of people before that point, and fellow Americans at that. Granted, the victims of the white phosphorous incident included forty-seven civilians, but even still...
Nice Hat: Sports a cap. The only time he's seen not wearing it is after he's just been lynched.
The Smart Guy: Given his role as both radio operator and translator, he is the first one consulted on technology or language.
Sound-Only Death: During a firefight with the 33rd and separated from Walker and Adams, Lugo tries to hole up in a refugee camp. And certainly, the soldiers don't find him...but the refugees do. Walker, Adams and the player all get to hear him screaming and pleading in a panicked mix of English and Farsi while the civilians form a lynch mob. He's dead by the time Walker and Adams arrive.
Sour Supporter: Gradually becomes this as the game progresses. After The Squad has committed a great amount of atrocities over the game, it's clear that the only reason he still listens to Walker is so he can justify his part in said atrocities as Just Following Orders. He is the most vocal opponent of the use of the white phosphorus mortar, and starts blaming Walker for involving Adams and himself right on the spot.
Vitriolic Best Buds: With Adams. The whole "best buds" part gets more doubtful over the course of the game - starting with the situation with Gould. When he dies, though, Adams' distraught attitude shows it wasn't gone.
Enemy Without: Walker acknowledges this in the epilogue, when he dons Konrad's uniform.
Evil Is Hammy: Konrad when communicating with Walker via radio is arch and melodramatic, often speaking in flowery figurative language, in sharp contrast to how he speaks in the occasional intel items Walker comes across, in which he is softly-spoken, matter-of-fact and dejected. This is because the Konrad Walker hears via radio is in fact his hallucination, and Walker is trying to convince himself that Konrad is a typical video game-esque Big Bad when in fact he is anything but.
Fallen Hero: Walker met him in Kabul (in fact, he owes Konrad his life) and says that he was once an honorable man. Konrad or rather, Walker's guilt in the voice of Konrad, notes that he isn't a hero just because he saved Walker's life; he has saved many lives, but as a soldier he's ended many more, and there's no real nobility in following a basic standard set by the U.S military.
Nice Job Breaking It, Hero: His attempt to help the people of Dubai led to the damning of the 33rd Infantry and the situation Walker has to try to clean up.
The Paragon Always Rebels: When he decides to help the people of Dubai, even in violation of his orders to do so, the entire 33rd Infantry go with him. Though not the entire 33rd, as the executed and hanging corpses of soldiers suggests, assuming they are real.
Reports of My Death Were Greatly Exaggerated: Inverted when the real Colonel Konrad is revealed to have committed suicide. When Walker discovers this, the Shadow Konrad, amused by Walker's reaction, says, "Looks like reports of my... survival were greatly exaggerated."
Smug Snake: Except really not. Collect the intel, and you will probably notice the jarring difference between the sneering, mocking villain that plays mindgames with Walker when ever he "speaks" with him, and the recordings of the soft-spoken, humble man the who is clearly horrified at the terrible things he has done.
You Can't Go Home Again: Konrad is very cynical about the ultimate fate of soldiers. In the Suicide by Cop epilogue choice Walker flash backs to a time where Konrad told Walker that all he desired was peace - but there was an inevitable line men like them would have to cross, with no option afterwards but to die bitterly on the battlefield. In a heartwarming contrast, the hallucinatory Konrad's final words to Walker in the game are a reminder to Walker that despite everything he's done, he still has the right to go home - basically challenging Walker to prove him wrong.
Cutscene Boss: When you finally reach him, he goes down without a fight.
Cynicism Catalyst: He became significantly more abrasive after the failure of the Dubai evacuation. Of course, it's shown at the very end of the game that what probably brought this about was Konrad's suicide.
The Dead Have Names: Tries to pull this on Walker and his team during the assault on his station. The problem is, even he doesn't really remember a lot of them.
Non-Action Big Bad: He goes down without a fight in a cutscene. Kind of a retroactive example, seeing as the revelation that Konrad was Dead All Along, and hence Radioman really was at the top of the chain of command, doesn't occur until the end of the game.
Pet the Dog: The Intel items that Walker finds indicate that he ultimately was concerned for the well-being of the citizens of Dubai - at least before the whole evacuation went to shit, anyway.
Sad Clown: Gradually revealed to be this to some extent, most notably after the water supply is damaged, where he's audibly shaken by the event.
Sanity Slippage: Some intel items reveal that he had a noble goal in his broadcasts, once — to keep hope alive in Dubai. That obviously got lost somewhere.
Smug Snake: During gameplay. Less so in the intel logs, where he's trying to get the truth about the situation out.
Troll: Has some shades of this. Especially with the interpretation that he is partly a mouthpiece for the developers.
The Stoner: When Delta Force finally reaches him, it's shown that he's been smoking a blunt - which more than likely explains his upbeat commentary to everything going on around him.
Surprisingly Sudden Death: Especially jarring because the tone of the scene and the surroundings is light, almost friendly - he could be any quirky disk-jockey giving technical advice. Until Lugo shoots him in the head three times at point-blank range, spattering the camera with blood. Even Adams and Walker are obviously shocked, forcing Lugo to start yelling in his own defense.
A Million Is a Statistic: His opinion of the refugees of Dubai; he cares nothing for their lives and goes so far as to lead them on to serve as Cannon Fodder in his plot to destroy their water supply and doom them all.
Jerk with a Heart of Jerk: The reason why he considers himself to be Good Is Not Nice is because he only cares about protecting his country from a war with the Middle East, rather than helping to evacuate the people in Dubai.
Knight Templar: Riggs believes his plan to kill the population of Dubai is absolutely necessary to prevent the Middle East from going to war with America.
Not So Different: Like Walker, Riggs believes he works to achieve a heroic goal (i.e. preventing a war between USA and the Middle East), and just like with Walker it is clear that he is completely delusional about the validity of that goal and the methods he uses to achieve it by only serves to make the situation much, much worse.
Manipulative Bastard: Manipulated the protagonists into getting rid of the water supply, leaving everyone in the city to die until and unless the unlikely event occurs that the rescue team comes in.