Port Royale 3

You can check your ‘Pirate’ status in the journal. It will be the red portion of the pie chart and can be increased by attacking a country’s ships and towns so long as you are not carrying a letter of marquee from another nation. 

TIP: An easy way to do this is to create a strong convoy (10+ warships with maximum sailors & weapons) and then prey on weak merchant ships. You can automate the battles to make it quicker. After roughly 15 minutes, the achievement will unlock.