Unlike most Assassin's Creed "100% Sync" achievements, this DOES NOT refer simply to the 6 story sequences.
This achievement requires you to complete:
-All story missions with bonus objectives (6)
-All Stories of Franciade and Murder Mysteries (6)
-All Co-op/Heist missions (2)
-All Sugar's Legacy riddles (7)
-All Outposts (3)
-All Viewpoints (3)
-All Artifacts (14)
-All Napoleon's Bicorns (26)
-All Chests (61)Sequence 13 (Story Missions)
Not my own video personally, but Centerstrain01 on YouTube has 100% guides for the story missions. Here's the link for the first memory. Go to their page to find the rest of the videos/be supportive of their efforts. Co-op
Co-op missions will not appear on your map until you have already done them once. To access them, go to "progress tracker" in the pause menu. These can also only be played in private (no public matchmaking) but can easily be complete by oneself if you have no co-op partner available.
The co-op mission is a straightforward "protect these guys while killing these other guys" sort of mission. Very similar to the one in the main game where you protect Napoleon. You do not have to get all 3 rewards from the Co-op mission.
I made a video showing an optimal entry method to the most optimal starting point. The objective is NOT always in the same location. Just enter through the window in the video, and head through the building until you find where the objective is. It moves every time you restart, so if it is out in the open courtyard or somewhere else you feel you may not be able to reach it easily, simply die or restart and it will move.
Tips for Heist:
-Always be sure to stay within the yellow area on your map so you don't wander too far into an area where the objective won't be. The building is not entirely covered in yellow.
-Use Eagle Vision repeatedly although the orange objective marker should appear once you are in proximity, with or without Eagle Vision active.
-You must be anonymous/out of conflict in order to open chest. Be extremely cautious when making your escape.
-If you die, you will fail, and if you go out into the open area in the middle, you will die.
-The escapes are much easier from the top floor than the ground floor
-Do not worry about your bonus reward (unless you want to worry about your bonus reward) as it doesn't count towards completion percentage.Outposts
Each of the 3 missions requires you to kill 3 targets. These can be tough, as they are completely surrounded by guards and have 5 diamond difficulty ratings. I recommend just stocking up on medicine and just running right into the fray and killing the targets. If you die, the targets you already killed will remain dead and you can move on to the next one.Sugar's Legacy
2 of the Sugar's Legacy riddles are part of the main story and are required to complete it. Video guides for the remaining 5 can be found on 360GameTV's channel here. Go to their channel to find the remaining 4 videos and to support their efforts.
The final wrap up mission "finis" does not count towards completion (although is required for the "Defender of Franciade" Achievement).
Here's also a link to the site I personally used for finding these for those who prefer text and still pictures over videos. http://www.gosunoob.com/assassins-creed-unity/dies-sugers-le...Collectables
Not all collectibles appear on the map at first, or after Viewpoints. You must pass near collectables before they will appear.
The various gold chests and pamphlets scattered around do not count towards completion.
I recommend, if it's not too late, to try to nab as many of the collectables as you can while progressing through the story, co-op, and Stories missions. This will lead to less running in circles later on and will allow more of them to be revealed earlier on.
Also, save these for last. If you play through all of the other missions and such first, you will have revealed the locations or found the majority of these naturally, without having to wander around aimlessly too much.
Progress can be tracked easily under "Progress Tracker" in the pause menu.
I have not personally found this site to be very helpful, but perhaps some of you might. Browse through it to find videos for all the different types of collectibles.http://www.vgfaq.com/assassins-creed-unity-dead-kings-franci...
Clear map of all underground chests
Not complete, but here are videos and links that show you maps with all underground chest locations and windmill locations (plus others) and all Artifact locations. Will continue to update as more complete maps become available. Videos by 360GameTV, NonStopTrophies, and VGFAQ respectively.