Drifting is a plaintive song used in the trailer for The Dentist, where the singer sings about regretting turning to crime and having to leave behind the life he once had. In the trailer it's used rather poignantly, indicating Dallas' mistrust of the police to the extent where he can't bring himself to claim the wallet he dropped after a cop picks it up.
I left my favorite cassette in the escape car / I'll never hear those songs again
It made me think of all the many things I've sacrificed / Oh mama, where do I begin?
Hector being the traitor made a few of his fans depressed, as his missions were among the most popular before The Dentist showed up. It would also mean that Hector would be the only contractor to not have any additional contracts made after the game's release.
"No one loves you Kelli, they are all afraid of you."
"Jim, you're the toughest of us. Me, I'll die young, I know I will."
The sheer desperation in Bain's voice should the Payday Gang fail a heist can be heartbreaking, seeing how he genuinely cares for them. There's also the fact that Bain places all of the blame in himself.
Bain: "WHAT?!NO! This isn't happening, my mistake! Next time I'll be better!"
Bain: "I checked everything! How did it go down like this?! I must have miscalculated something here, forgive me!"
Bain: "Goddammit! That wasn't supposed to go this way! I should've seen this coming. I must be getting old."
Bain: "Oh this is just totally FUBAR! Must've been my plan! Sorry people, I messed up."
Even worse is the failing heist message for the White House heist, which is already a tear jerker in its own.
Bain: "Hey gang... sorry to get all dramatic on you, but... looks like they got me, and... you've got to assume I'm dead. Should have paid more attention in Vegas. Locke has probably filled you in on some things by now... I didn't want to keep you in the dark about this secret society crap, but there was a lot I didn't know. If we played it right, this would have been the end all... to give us everything we ever wanted and keep the cops off our asses for good. I figured things were gonna get easier when Duke came in to help with the missing Lindenhurst pages of Cagliostro's book, and this watcher business... after all, his family has been knee-deep in this stuff from the start, but this is bigger than us. A lot bigger. So you've got to make a choice. Either retire to an island somewhere, let the world sort itself out and hope this shit doesn't follow you... or keep going, help Locke finish what I started, and find Baldwin's lament. Remember guys, whatever happens... trust your partners. And Jacket, don't you go hogging this tape, it's not just for you."
It's been implied throughout previous missions and the FBI Files about how Bain's health has been deteriorating. In the heist, you actually get to see him and how badly he's hurt from all the torture that has happened to him, and he sounds so drained when you manage to catch up to him after barreling his way through Murkywater's forces. Considering how Bain interacts with the crew before these events, it's quite saddening to see him be reduced to this state.
The fact that you meet Bain in person for the first time seems like things are looking up for the gang... and then he promptly collapses due to a virus of some kind. Locke appears promptly afterwards, picks up Bain, and struggles his way to the helicopter, carrying Bain all the way despite all of the strain it seems to be putting on him.
Kento was the last victim in Bain's path of destruction after he is let out, confirmed by Bain himself to be dead. If Jiro's attempts to reconcile with his son weren't well and truly impossible before, they are now.
Locke tiredly mentions after the mission is over that Bain is being treated and that he has some sort of man-made virus (which will no doubt require a cure of some kind). It's strongly implied that whatever the Kataru did to him, Bain is now dying because of it. Locke even sounds like he's on the verge of tears when he angrily states that the Murkies and the Kataru will pay dearly if Bain does die.
The outcome of the heist itself can be considered this, in a way. Bain is now on his last limbs and possibly dying, Jiro has lost his son (to the man he called his new boss, no less), and with the appearance of The Diamond among some bakery goods in the Safe House as well as The Dentist answering a phone call intended for The Elephant, both he and Vlad are MIA until shown otherwise. Despite what the gang managed to achieve, it's hard to tell if the Payday Gang truly won in this heist.
The worst part of all this? On the mission select screen, if you pick No Mercy, you hear Chains talk about how that heist years ago was very shady from the start due to Bain taking on the job in exchange for the Guide of Cagliostro. Chains also says that he wanted to tell Bain to fuck off because the job didn't sound right, but he went with it in the end since he trusted him and if it weren't for him, the crew would not be where they were today. You can tell that Chains is upset that the person that was basically their mentor is dying and how Chains could have possibly prevented this years ago if he had just said no.
The ending. The gang is able to secure their pardons from the White House, but Bain succumbs to his illness and dies whilst delivering his debrief for the heist. The gang holds a funeral for him somewhere in Mexico, during which everyone throws their masks into his grave (with the exception of Jacket, who throws in his tape recorder) as one last gesture of respect for their boss, before going their separate ways and retiring to a normal life. Everyone except Dallas, that is. Without saying a word, Locke gives Dallas a salute as if to say he did the best he could, and then leaves. Dallas takes his mask off, but doesn't throw it into the grave. The PAYDAY gang won in the end...but at what cost?
As for beating the White House heist, you'll hear Bain's Famous Last Words before he pass away from the virus. It may count as Heartwarming Moments while he admits to be proud of them for pulling an impossible heist:
Bain: You... did it guys. Y-you pulled it off, the damn White House. I'm proud of you, damn proud. Now you're free, free to- *Groan* Is- is this? Oh my...
It's made even worse by the current situation that the game ends on: Bain is dead, which likely means that Crime.net will either be heavily crippled or shut down until someone like Locke can steady the ship, it's currently unknown what will become of the crew (or if any of them are going to return to their life in the PAYDAY Gang in the future, since Bain's death might have made some of them lose their will to fight), Jiro has lost his son and the man he considered his new boss weeks, if not days apart from each other, The Dentist, Murkywater and the Kataru are still at large, most of Crime.net's other contractors have gone under radio silence, and the President of the United States is confirmed missing following Air Force One's crashing in California. Were if not for the fact that the gang managed to steal presidential pardons straight from the Murky-infested White House and seal their spots as Karma Houdinis, this would have been a straight-up Downer Ending where the Kataru, Murkywater and The Dentist essentially win. On the bright side, this isn't thetrue ending, and isn't considered canon in any way.
A rather meta example: After 5 years, PAYDAY 2's story has finally come to an end. As the result, some players may feel a bit teary-eyed...