Here is the full list of all 14 Bridge Constructor Medieval achievements. It takes around 2-3 hours to unlock all of the achievements on Windows.
Score is 250,000 points or higher.
Earned all crowns!
Score is 100,000 points or higher.
Earned 30 crowns!
Built a bridge with at least 100 components.
Score is 50,000 points or higher.
Undercut crown budget by 3,000.
Plunged a total of 50 enemies into the abyss.
Rescued 30 of your own units from enemy fire.
Rescued 15 of your own units from enemy fire.
Plunged a total of 20 enemies into the abyss.
Undercut crown budget by 1000.
Earned 20 crowns!
Earned 10 crowns!