Resident Evil 7 has two endings. Which one you get entirely depends on a single choice. It may present itself as a dilemma: good vs. good, but I've seen the two endings and I can say that there's really only one ending that you want to get. The other one just leaves you regretting that choice.
[Spoilers beyond this point] When you eventually create the serum that will cure those who were infected by Eveline, you will face a "tough" choice: give it to your wife Mia, who's the reason why you went there in the first place, or give it instead to the innocent Zoe Baker who had been a great help to you. Here's how the ending will play out depending on your decision.
Resident Evil 7 Ending 1: You Give Mia The Serum
This seems like the most sensible choice isn't it? You ended up in the Baker mansion, triggering the whole storyline of Resident Evil 7, because you were looking for your wife. You eventually find her but she's infected. You are given a choice to save her with the serum or don't. So, why would you not give her the serum?
When you make the choice to give her the serum, she will go with you on the boat to Louisiana. However, Eveline will trap both of you. At this point, you will be able to control Mia to save Ethan, the Resident Evil 7 protagonist. Eveline will try to control her, but since she was given the serum, she will be able to resist. She will then lock herself in a room and Ethan will successfully escape, leaving her behind.
In the Resident Evil 7 ending after the final boss fight, an Umbrella Corporation helicopter will come to save you. You will meet an agent named Redfield, but we don't know if he's THE Chris Redfield yet. In the helicopter is your lovely wife waiting for you.
The bad in this ending is that you don't know what happened to Zoe. There's the sliver of hope that she may have survived. But, should we have chosen to give her the serum instead?
Resident Evil 7 Ending 2: You Give Zoe The Serum
We get it, you're not like the monsters in the Baker mansion. You have conscience and compassion, especially to the cute and innocent Zoe. So instead of your wife, you should give her the serum. Who knows, your wife might have another chance as the story progresses, right?
Wrong. This choice doesn't give you another Resident Evil 7 good ending at all. It's just a downright bad ending. She will go with you on the boat, but Eveline will straight up kill Zoe because she doesn't like her. What a waste of the serum.
Then, you will be trapped again and Mia will come to the rescue. And since she was not given the serum, Eveline will be able to control her and next thing you know, your wife is trying to kill you. You will then be forced to kill your wife.
The rest of the ending is pretty much the same. You get to the last boss fight, a chopper comes, someone introduces himself as Redfield, but no one is at the helicopter. I quite agree with Ethan's monologue: "It was all a failure."
With that said, I'm quite disappointed that we don't have a real dilemma here. There are only two choices: alive Mia and possibly dead Zoe OR 100% dead Mia and 100% dead Zoe. I guess we now all know which choice to make, unless we don't want the Umbrella girl who brought us to this mess as a wife anymore.