- Estimated achievement difficulty:3/10
- Offline: 50 
- Online: 10  Note that only 4 of them require online connectivity, the others can be done in the multiplayer mode using solo Wolfpack gameplay.
- Approximate amount of time to 1250: 45-60 hours
- Minimum number of playthroughs needed: 1 [can do mission select if needed for full synchronization]
- Missable achievements: None
- Does difficulty affect achievements?: No difficulty settings
- Unobtainable/glitched achievements: None
- Extra equipment needed?: None
DLC: Blackbeard's Wrath
- Difficulty: 1/10
- Time to 80: 1 hour if boosting. Potentially much longer if playing random matches
- Unobtainable: None
DLC: Freedom Cry
- Difficulty: 2/10
- Time to 170: 4-6 hours
Assassin's Creed IV: Black Flag is a prequel to Assassin's Creed III, but while it is set in the Assassin's Creed universe, it is mostly a pirate game. If you go into the game with that mindset rather than expecting a game about assassination and stealth, you are likely to enjoy it much more. You play as Edward Kenway while in the past, and as an anonymous Abstergo employee while in the modern era. There is a large focus on naval combat as well as some new mechanics such as swimming while submersed. Overall this is a very well done naval warfare/pirate game that has some peripheral ties to the prior Assassin's Creed games through the main storyline and the modern era scenes.
In order to unlock Sharing is Caring, you have to be online during the campaign. If you typically play offline, make an exception for this game at least until you have this achievement unlocked.
All of your time spent in the modern era is pretty linear and scripted. There are very few achievements tied to this, so enjoy the story for what it is, hack every computer you can find, and get back into the animus. Most of your time will be spent playing as Kenway, and initially you will want to move through the objectives and not worry too much about exploring or other tasks until you complete Mission 6 Sequence 1. Try to complete all of the secondary objectives for each mission to minimize the number of single-mission replays you will need to do later. Along the way upgrade your ship as best you can so that you are more able to easily defeat the early naval enemies. While on land, the one thing you will want to do early is to synchronize any viewpoint you can. The viewpoints turn into fast travel locations which speed up game play later. In addition, obtaining all secrets in each area is useful to ensure you get all the treasure maps.
Once you have finished Mission 6, Sequence 1, you are able to dive on locations of sunken ships. At this point you will want to wait on advancing the story any further and focus on capturing ships, maxing out Kenway's Fleet, and upgrading the Jackdaw to the maximum you have access to. There are a few upgrades you can't access until further in the story, but most of them can be obtained at this point, you just need to find the blueprints. This is a good time to get most of the locations explored as well as capturing all the forts. There is a clever way Spanish Assault found to easily obtain man o' wars for Kenway's Fleet detailed here.
Kenway's Fleet is controlled from the cabin of the Jackdaw, and missions there take place in real time. Friends can help speed things up, but much of this will be spread across a week or so of game play. Kenway's fleet is your primary source of income in the game, so bigger, faster, and stronger ships are important. Make sure you expand out to the full complement of ships as soon as you can, and keep upgrading the ships you use by replacing the smaller ones. Keep 2-3 schooners with fast attack times, 2-3 frigates with fast attack times, and then all the rest should be man o' wars with a focus on larger cargo capacities. Use the schooners and frigates to clear the sea lanes when you are facing small ships just to prevent having to repair your man o' wars all the time, and then send your ships on the most profitable routes. You should ensure that you sail each route at least once to unlock all the content in the game, including one of the plans needed to fully upgrade the Jackdaw.
Next, it is time to jump back in the game and finish up the story! Again, focus on 100% secondary objectives and visiting any new locations that unlock. I would avoid the legendary ships that are located in each corner until the end of the campaign. Throughout the story keep checking Kenway's Fleet to keep money coming in. After the story is done, the game becomes a large sandbox and you can visit all locations as needed. There are quite a few miscellaneous achievements that will need to be finished up such as Killer Killer and Vault Raider, but they are generally straight forward and should offer no particular challenge. Finally, tackle the legendary ships to finish up the single player!
The multiplayer will require you to try every game mode at least once and also use every ability and ranged weapon available in MP. This means purchasing and equipping them, or using the copycat power to use them. Obviously, it is more reliable to purchase them as otherwise you are dependent on other players to actually have what you are looking for. You also have to level up to 55 in the multiplayer which will take some grinding. You can do your leveling in Wolfpack solo or with a group if you prefer that over competitive multiplayer.
These are all multiplayer achievements that can be earned in a public match with some skill and patience, or you can get a party together and rip through them all in about an hour. Alternately, all of them except Sacred Land and Elevator to the Gallows can be earned in single player Wolfpack. I strongly recommend the later approach. Note that you must be level 38 before you can complete all of the achievements unless you spend real money as a microtransaction.
There are two achievements for completing the story: Liberation Day and His Word Was Perhaps. You also will need to get full synchronization on the story missions to unlock His Full Attention and His Own Medicine, and will also unlock Firepower at the same time (although it can be unlocked earlier). The last achievement is obtained by freeing 500 slaves, which you can do at any point in the game after starting Memory 2. The entire DLC should take no more than 5-6 hours.
This is a fun pirate game in the Assassin's Creed universe, and adding in the trading meta game gives a different flavor to interacting with your friends. Overall it is a relatively easy completion, albeit with a bit of grinding for the multiplayer.
Many thanks to Morbious17 who started an alternate guide, from which certain facts and figures were borrowed, and to Capn Doug for providing a plethora of critiques and adjustments.
[XBA would like to thank Creech for this roadmap]