Here is the full list of all 26 Braveland Pirate achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Fulfilled all the assassination contracts.
Have won 150 battles.
Have overcome 25 random encounters in the sea.
Looted all treasure chests and hidden caches.
The Great Reaper defeated.
Game completed without using the easy level of difficulty.
Game completed using only the hard level of difficulty.
All the bosses defeated.
All pirate tricks learned.
Obtained the old man's artefact in the sea.
Visited all islands.
Rejected all the assassination contracts.
Jarl Erik defeated.
Have answered all the questions of the sages.
Rejected the Iron Bank's offer.
Sir Rodrick defeated.
Six pirate tricks learned.
Fought through all dungeons and arenas.
All four equipment items on.
Davy Jones defeated.
Bought an item for hero.
Page on Facebook or Twitter visited.
You defeated the army without losing a single warrior.
Pirate trick learned.
Looted 7 treasure chests and hidden caches.
Cabin boys have joined you.