In this video guide I will show you how to proceed with caution and avoid unneeded damage in mission 15. All you need to avoid is the spikes coming from the walls, ceiling, and floor for the first part of the mission. There will be some enemies in an area with no spikes so I would advise to try and fight them there so there is no accidental being knocked into the spikes.Once past the enemies and into the open room where there are more enemies you are clear the rest of the mission. The achievement will pop once you beat the level.