Going on a killing spree in an RPG is nothing new, but there's often a limit to your reckless carnage. Typically in RPGs there are NPCs marked as Essential, and they're usually quest-givers. After all, if you deliberately or accidentally kill someone who can send you on a quest before they send you on that quest, you won't be able to complete it. For a side-quest, you'd be out of luck, but for a main quest, you'd be completely stuck.
Speaking to Polygon, Obsidian's senior designer Brian Heins confirmed that in The Outer Worlds, you'll be able to kill anyone you want. And to protect your ability to complete quests, there are back-up systems in place.
“Anyone you see, you can kill, [so] there’s got to be a way to get whatever they were going to give you, whether it’s a terminal entry or you can loot something off of their body or there’s a chest in their office that you would now lock-pick to get the information from," Heins told Polygon.
That often adds more complexity to the quest because it may need to be reflected in dialogue further down the questline. If you kill a quest giver and loot their body or pick a lock on their safe to acquire the quest item, for example, another NPC involved in the storyline can't talk about how you were freely given that item by the quest-giver. Because it didn't happen that way.
It's a lot of extra work for the designers and writers and even the QA department, who stumble across bugs as a result of the added wrinkles to the story. "So a conversation that they started out writing as very compact and concise now starts growing much bigger, because they have not had to handle a lot of other states,” Hines said.