Revenge Before Reason: Bohannon overrides any sense of self-preservation or logic if revenge is the reward. This in particular blows up ons his face when he murders a innnocent man because of the illusion this man killed his wife.
The Sociopath: He isn't even close to being this, but expresses fear of becoming one after not feeling guilty for his brutal murder of an innocent man.
Corrupt Corporate Executive: His Corrupt Corporate Executive credentials are all Truth in Television. The real Durant did set up Credit Mobilier to pay himself for building his own railroad, he did use "oxbow" curves to arbitrarily increase the length of the railroad and get more government money, he did bribe senators, and (as mentioned by Bohannon in their first meeting) he did make a lot of money smuggling embargoed cotton out of the Confederacy during the Civil War.
Face-Heel Turn: He was always something of a Jerkass with some soft spots, but as of the third season, he has also decided to destroy Bohannon. Most of his Pet the Dog moments also vanished with the death of Lily Bell.
Jerkass: While he has can be quite a gentleman, Durant cares about profit first and foremost, and he loves to remind people of such.
Large Ham: Half the appeal of the series is watching Colm Meaney chew the scenery.
Manipulative Bastard: As his interactions with Senator Crane demonstrate, Durant is a master of psychological manipulation.
Pet the Dog: Most of his interactions with Mrs. Bell show his kinder nature. Kick the Dog: Then he tries to have her killed
Pragmatic Villainy: Durant he seeks profit, and nothing more. He won't go out of his way to be evil if it doesn't involve acquiring posessions. However, the same goes for being good.
Took a Level in Badass: Multiple. He starts the series as a common worker of Durant, but after some bouts with the Irish and Bohannon's training, Fergurson becomes a expert marksman, second only to Bohannon himself in Hell On Wheels.
Damsel out of Distress: Lily Bell stabs the man who killed her husband with his own arrow, treks however many miles alone and sews up her own wound before she's rescued.
Determinator: Crawled through some five miles of mud, with an arrow wound on her hand, starving and without water, as she was pursued by Indians. Most people would go home and rest after such a experience. Mrs.Bell instead went right back to work.
Guile Heroine: Lily is clever enough to impress Durant, and is matches him in knowledge of economics and psychology. A fitting example being when she escaped a murder attempt by convicing the assassin to side with her.
Only Sane Man: The matter is Indians where he is the only person to even consider the possibility of peace.
Preacher Man: Started off as this, gets more ambiguous as season progresses.
Sanity Slippage: After the Cheyenne Attack on the railroad, he becomes unhinged and becomes alcoholic. It only gets worse and worse from there.
Straight Edge Evil: Played with. He starts his sanity slippage and descent into evil by drinking himself to oblivion, but is little more than a Cloud Cuckoo Lander at that point, he only becomes truly evil after he stops drinking.
The Lancer: Becomes this for Bohannon in season 2.
Last Name Basis: His first name was never mentioned. until his funeral, that is.
Pet the Dog: When he finds out Eva is pregnant by another man. He figures out that it's Elam but instead of killing one or both of them gives Elam a What the Hell, Hero? speech and returns to comfort Eva, apparently willing to accept the child as his own.
Odd Friendship: With one of the black workers (keep in mind this man tried to hang Fergurson for no other reason other than being black a few episodes before). It was the result of his Heel-Faith Turn after Elam's bullet incredibly didn't kill him.
Played by: Gerald Auger
Cain and Abel: The Cain to Moon's Able because of his extreme measures.
Beware the Nice Ones: Just ask the Butcher (whom he butchered) Or Carl (whom he blackmailed for being an asshole).
Brains and Brawn: Sean is the brains, Mickey is the brawn. This is Lampshaded by Sean early in the second season. The dynamic is played with later, when Mickey acquires a better sense of judgement than Sean in a few occasions and fully subverted in Season 3 where Mickey becomes far more intelligent than Sean, who is much more prone to mistakes.
Cain and Abel: Season 3 sees the brothers getting increasingly more antagonistic towards each other. In the end, the Abel kills the Cain: Mickey shoots Sean when he gets out of control.
Did You Just Flip Off Durant?: Mickey is a pimp, Durant is a master manipulator and one of the wealthiest and most influential men in America who could destroy him with a flick of his wrist, yet Mickey is not afraid to lay the verbal smackdown on Durant, and he barely flinches when Durant makes his (very serious) threats.
Nice Guy: Mickey treats everyone with respect and a warm smile.
Noodle Incident: Mickey did something in Boston. We're never told what, exactly. Until season 3's "It happened in Boston", in which Mickey explains to us that Sean fell in love with two girls, did some horrifying crime to both of them in a fit of rage.
Not So Different: Sean had a burning hatred for the Swede and his way of doing business, but after the Swede is down, he ends up conducting business with the same methods. He does not realize the similarity.
Corrupt Hick: Despite being a northerner and an Immigrant, he fits this trope to a T. When he's not out being the Hanging Judge, he's shaking down businesses and bribing officials to look the other way while he robs his employer.
The Corrupter: Cole already had a few problems before him, but it was The Swede who gave him his final push into villainy. Also attempts this on Bohannon for very little reason other than "why not".
Evil Counterpart / Foil: As the man himself notes, The Swede is, essentially, Bohannon's dark side personified: A ruthless murderer addicted to battle itself. He is a constant reminder of Bohannon's capacity for evil.
Made of Iron: Shrugs off third-degree burns without further thought after an afternoon of rest. And then he comes back, even though he fell off a significant height into shallow water, in a shot that heavily implied he died on impact.
Establishing Character Moment: He walks out of a train, sees a thief robbing a man, promptly beats the thief down and gives the man his walllet back. This establishes Declan as a man of old-fashioned values in the crapsack world that is Hell on Wheels.
Intrepid Reporter. She is at Hell On Wheels to cover the building of the railroad and does so as honestly as possible
Lipstick Lesbian/Ambiguously Bi: She got shipped out west at least partly to keep her away from her boss' daughter but she didn't seem to mind when Bohannon kissed her either. She didn't really respond but that could have been just because she was shocked and surprised.
Unwitting Pawn: Durant pointed her towards the murders Bohannon commited in revenge and then used her story against him at the trial.