These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Complete Monster: Miguel Bain stands in marked contrast to protagonist Robert Rath. Where Rath has standards about the people he assassinates and abhors hurting innocents, Bain has a penchant for indiscrimately slaughtering everyone who gets in his way. In the first mission we see him on, he kills the target and his bodyguards, then kills several police officers to escape from custody. When Rath later traps him in the back of a car, Bain prepares to snipe a nearby child to make Rath back down. During an exchange between a hacker named Electra and a group of Dutch clients who turn out to be Interpol agents, he blows away every agent and bystander he runs into and promises Electra that he'll personally cut out her heart. Rath saves Electra, but not before Bain kills Electra's two downstairs neighbours for no real reason. Bain eventually reaches an understanding with his anonymous employer to kill Rath himself, whom he perceives as an irritating rival. Even when Rath offers Bain the opportunity to part ways peacefully at the end, he elects to kill both Rath and Electra instead. Having no regard for any life he takes, Bain became a contract killer largely for glory and thrills.
Cry for the Devil: The three ballads are used effectively in this way, but the one that seems to get the audience's sympathy most is "The Ballad of Czolgosz", where assassin Leon Czolgosz's motivations are stated clearly: he was a lonely man, who all throughout his life had lived in poverty and misery for reasons beyond his control, so he killed big business president Bill McKinley to "take control of his fate".
Nightmare Fuel: The end of Lee Harvey Oswald's scene, when all the assassins surround him singing about how much they admire him while he loads his rifle and prepares to shoot Kennedy. The Lyrical Dissonance and the menacing sound of the melody make it especially creepy.
One-Scene Wonder: Depending on the direction, The Proprietor may pop up throughout the rest of the show, but he's only scripted for the opening scene, leading "Everybody's Got the Right". In the original production, Lee Harvey Oswald was this as well, though ever since the 2004 Broadway revival, it has become common practice to double him with The Balladeer.