6 achievements not missable, if you finish the game you will unlock those.
The 2 missable achievements require finding some secrets during the level on Undergrounds.

Once you will arrive to the Undergrounds level (once you used the vent in the house) you will land in a room with an oil lamp. When you will head out of that room go left, follow the wall and you will get to a room with bookshelves. When you enter the room take the most right path between the bookshelves and at the end you will find an energy drink:


KEEP THIS ENERGY DRINK! Do not use it. So you keep it in your inventory.

Now you will need head to upstairs, to a room where you will find the storage key which will be required for storyline progression (key is at the green marked area).


For both missable achievement you need to enter the vent on the picture. Jump first to the table, then the chair then the lamp. From there you could jump to the top of the bookshelf and enter the vent. It is pretty annoying, just keep pushing W while on the lamp and facing the wall, while spamming C+SPACE buttons.

At the end of the vent you will find a room with a skeleton which unlock:

My Collegues

achievement, and when you have the energy drink in your inventory, then you can unlock the door in the same room for:

#ad

achievement.

Enjoyable games on an achievement hunter curator with perfection times, difficulty ratings, some helpful info about the games and linked guides/reviews/walkthrough videos:

https://store.steampowered.com/curator/30168383-Average-Achievement-Hunter/

If you extra thankful for the guide please follow the social media links on the curator too (twitter, YT):-D
Thanks