Life is Strange: Double Exposure

You will get a favor if you complete the small task of mail retrieval for Vinh in Chapter 1.
In Chapter 2 when you are exploring the school you will need to do Vinh's quest to the point he forgets his phone password. Shift worlds and talk to Dead Vinh to try and get the code. When asked to cash in favor say "not yet" and this achievement pops.

In chapter 1: back to school blues you will have a secondary objective to find a package for Vinh. You can find this in the mail room and upon returning it you will be informed that he owes you a favor. To get this all you have to do is not cash it in for the whole game. Considering there is only one opportunity to cash it in this is a very simple requirement. The opportunity will happen in chapter 2: by the horns, when given the objective to talk to Vinh in the dead world you will eventually be given the option to cash it in or not. By not cashing it in you will earn this and there's really no reason to avoid it since both options lead to the same place. Visual guide for this description can be found below: