Hellpoint

Here's the step by step guide from Steam:

https://steamcommunity.com/sharedfiles/filedetails/?id=21935...

· One small step: Repair the EVA suit and walk in space. – For this achievement, you have to first find the Broken EVA suit armor set. This is located inside a hidden area inside the Embassy, just before you fight the Archon Slayer. In the Embassy hall leading to the Archon Slayer boss fight, run to the opposite end of the hall to a gate that you may have opened, that leads back to the beginning of the game. To the left of this gate in the hall is a hidden wall, which looks like 3 rectangles, press X on controller to interact with the middle wall and open it. Follow the path down a few floors, fighting Flying Fish and Tool Victims as you go, and once you reach the bottom floor, you’ll find a door that leads out into space. Once you get inside and activate the air lock, you’ll begin taking Radiation damage and oxygen damage, so you must go quickly. Follow the path in space outside to the corner, and turn right, you’ll find the Broken EVA set. Next, you’ll need to find the Model: EVA blueprints to repair the set, this can be found in Arcology Underside. From the first Breach in Arcology underside, turn left, and you’ll find it at the end of the gallery. Return to the Observatory, and craft the EVA set, then return to where you found the broken EVA set in the Embassy and go outside wearing it, you should get this achievement.

Also here is a video to know it's exact location early game.

All credit goes to Zeroster:


Here's a link to the Hellpoint Wiki for a guide for Arcology Underside.