This guide is somewhat flawed, but still hopefully useful guide for achieving all the endings in the game. This is based to some extent research and some extend guesswork, so I might somewhat wrong in some aspects.
This endings requires you to hide Kim during the “letter” quest. To do so you must have a free house to hide Kim. Then you must help her survive (get her food, prevent cop from arresting her, get her warm socks and money). Eventually you must help her escape, by getting the foreign band manager help you (you need money and diplomatic passports, later of which you can get from lady in office 401). According to Jeddy No snound, you can also get the passports from someone else in the department.
Then, as you are about to escape Frank’s wife arrives, and tells you that she will report you if you try to escape. If you just try to escape both you and Kim get caught (bad ending), or you can stay behind and let Kim escape, at the cost of Frank spending last of his days in prison. (good ending).
For Hardliner endings you must side with them (I thing the important thing is framing the foreign band manager, which you can do by hiring prostitute (Nora), and getting it on camera/peeping on the event). Then you must not help Kim during the letter quest, and then when Kim calls you must ask the short lady from department V to help you. Then just help her till she orders you to arrest the reformist from department V. For bad ending, at the last moment try to betray her, for the good ending follow orders. Not sure if who you purge in the end affects which ending you get, but just to be safe purge any and all reformists from government.
This is the part where I start really speculating, since I have yet to go for the last two endings, but I think I can give you a fairly accurate picture.
For this side with the reformist (so don’t send the short lady any blackmail material on the foreign band manager), let Kim get arrested in the letter quest and then when she calls for help work with the reformist leader to get Kim free. The follow his orders to the end for good ending, or try to deviate from them near the end for the bad ending.
Again, I am speculating a lot here.
So you need to help the lady from office 101 in the bottom floor when she asks you to find some file. Find it, and then she asks you to show it to Wolf. Then follow Wolf’s orders (get Müller to say that he could get Wolf’s wife’s information, break into his office and find his password and go to floor 3 computer to get the information you need). During the letter quest do not help Kim, then when she calls go to Wolf for help. Then follow his orders to the end for good ending, or try to deviate from them near the end for bad ending.