Here is the full list of all 18 Prison Architect achievements. It takes around 50-60 hours to unlock all of the achievements on Windows.
Unlocked all polaroids
Stopped a riot of 50 or more prisoners
Executed a prisoner on death row
Build a sandbox prison with 1000 prisoners
Unlocked all game bible pages
Complete optional objective on Bootstraps
Complete the story
Complete all optional objectives on Conviction
Complete all optional objectives on Riot
Escape from a decent prison in escape mode
Loaded a prison from Steam Workshop
Shared a prison via Steam Workshop
Have a cashflow of $50,000 or more
Build a sandbox prison with 500 prisoners
Sell your prison and make over $1,000,000 profit
Unlock entire tech tree
Build a sandbox prison with 100 prisoners
Achieve a re-offending rate of 25%