This single achievement will takes some time (15-40 hrs+ depending on your platforming skill) as you need to get SS rank on every standard stage to unlock the 16 red keys required to unlock the ! levels. This achievement unlocks upon SS rank of the Giga Difficult level in that set.
To get an SS rank you need to beat each level getting all the dust cleaned in one combo, which requires not getting hit by enemies or spikes/falling.
I have provided videos for all levels SS ranked (including giga difficult), which provide as safe paths as possible, which may be easier to follow than the top speed replays. Good luck!
Forest SS
Mansion SS
City SS
Lab SS
Giga Difficult SS