This achievement requires meeting 25 level targets.
There are 4 targets per level:
1. Completing the level.
2. Completing the level with 100% Mercury level.
3. Collecting all bonus items in the level.
4. Completing the level within the time limit.
You do not need to meet all of the targets in one pass, it may be easier meeting the time target if you skip bonus items. So far I found one bonus item easier to get after spilling some mercury off the side.