Spoilers ahead for quest Out of the Fire.
If you have not done that quest and want to go do so now. I will still paraphrase and keep info generalized, but still.
So I just did the quest Out of the Fire and it started off okay.
"My son ran off with some raiders and took my grandfathers heirloom that is so cherished and dear to us. Can you bring it back?"
'Sure thing.' - Get heirloom, optional get son back.
So you go and fight the Forged. Bunch of raiders obsessed with fire. Anyway you get to the top and there is the big boss and his goons trying to get Goodboy son to murder a settler and kick them into a pit of fire.
Bigboss says as you enter:
"Who the hell are you? How did you get past all my forged goons?"
'I heard you were having a barbecue and you didn't invite me.'
"HA! You see Goodboy, this is my kind of person. You could even be Forged material."
(That line there sparked a glint of hope in bad guy story)
"You have to the count of 3 to kill that settler Goodboy. 1... 2..."
At this point I ran the options through my head. In past games, FO:3 and New Vegas, we have seem missions like this before. Raider boss was impressed with my killing ability, so what if I kill the settler? By the logic of passed games boss was impressed and said I could have what it takes, I kill prisoner, boss offers me place with them, new bad guy quest line opens up! I was convinced this was going to happen!
Spoilers, it didn't.
Boss just aggros as soon as you kill them.
"How dare you murder the prisoner that I was just now trying to have murdered. I'll murder you!"
* sarcasm *
tl:dr
Mission Out of the Fire was a missed opportunity for being bad guy because FO:4 is GOOD GUY ONLY! You can be an angry jerk, but no bad guy like in past games.
Oh almost forgot!
"Thank you for getting our grandfathers most treasured heirloom that we cherish so much in his memory back... I give it to you as a reward."
'Yup. That' wonderful.' - Drops it immediately in front of him.