When the Assassin's Creed franchise first broke onto the gaming scene, it was a unique combination of open-world traversal, stealth gameplay, and historically-accurate narrative. That was in 2007. Now, 15 years later, Assassin's Creed is one of the biggest gaming franchises in the world and has a noticeable influence on nearly every open-world video game that hits the market.

RELATED: Assassin's Creed Rift Needs Excellent Parkour

While fans of the series are drawn in by its stunningly-realized historical settings, satisfying parkour mechanics, and unusual sci-fi meta-narratives, the games have long struggled with their mission structure. Nearly every Assassin's Creed game feature missions that require frustratingly-specific criteria to complete them, particularly for players seeking 100% synchronization. Here are some of the worst offenders in the franchise's history.

10 Black Bart's Gambit (Assassin's Creed: Black Flag)

Assassin's Creed Black Flag Black Bart's Gambit

For players breezing through the game, this mission isn't too much of a hassle. Anyone trying to achieve 100% sync, however, is in for an agonizing experience. The goal of the mission is to commandeer a Portuguese ship, with 100% completion requiring Edward to stay out of combat and to assassinate the ship's captain from a rope swing.

The problem is that the assassination only becomes available right at the end of the 20-minute mission. Rope swing assassinations are hard to pull off, requiring the near-perfect timing of both jumping and executing the assassination. Mess up either one, and not only will Edward fail that objective, but he'll land smack in the middle of the ship's deck and fail the other optional objective as well, requiring players to go back to the start of the mission to try again.

9 Caress Of Steel (Assassin's Creed Rogue)

Assassin's Creed Rogue Caress Of Steel

The first part of this mission isn't too bad, but it all goes downhill once Shay is poisoned at the midway point. The poison causes Shay to take damage when he's moving slowly or standing still. While dealing with this, players must then attempt to locate a character named Hope.

RELATED: Assassin's Creed Should Tell More Stories Following Templars

Hope is, of course, found in an area chock-full of enemies. If Shay tries to avoid combat, he'll inevitably take damage from the slower pace of stealth. If he engages in combat he'll take damage from, well, the combat. Making matters worse is the mission's optional objective, which is to stay out of combat, causing the poison even more frustrating.

8 When In Rome (Assassin's Creed: Brotherhood)

Assassin's Creed Brotherhood When In Rome

How about a mission that's not only frustratingly difficult but simultaneously mocks the player for not completing it faster? Ezio, after disguising himself as a Roman guard, must transport a chest of money across Rome. However, he must do so without a map marker or an NPC to follow.

Instead, the only way to know which direction to travel is via the comments of various Roman guards. Basically, the guards will call the player a fool for going in the wrong direction and will say positive things when they're going the right way. That alone is torture, but now consider that the mission's optional objective is to complete it in under 3 minutes, meaning players will have to run to their destination. Don't hit an NPC though, or Ezio will drop the chest.

7 Sibrand Of Acre (Assassin's Creed)

Assassin's Creed Sibrand Of Acre

Every assassination in the original Assassin's Creed had its share of frustrations, but the mission to take out Sibrand of Acre was on another level. While other targets were located in castle keeps or inside military camps, Sibrand is located on a boat. Altair is blessed with a wide array of skills, but unfortunately, none of them are swimming.

Instead, Altair must approach his target via a series of conveniently-placed fishing boats, docks, and small wooden posts along the water's surface. One missed jump sends Altair plumetting into the water and forces a restart. If that weren't bad enough, Sibrand has archers placed all around his boat, and if one of them spots the incoming assassin, that fails the mission as well. The actual assassination of the target is relatively straightforward, but getting to that point is a nightmare.

6 Return To Mexico (Assassin's Creed: Liberation)

Assassin's Creed Liberation Return To Mexico

This is a unique situation where the majority of the mission is standard Assassin's Creed fare, no more difficult than anything else in the franchise. Yet it briefly introduces one new mechanic that is a total disaster: canoeing.

Aveline is seeking the second half of a Prophecy Disk, and her mother points her to a canoe she can use to get downstream. Getting to the canoe is easy, but controlling it is another matter. There are various obstacles scattered along the river. Hit too many, and the canoe sinks. On its own, that's not that bad, but the canoe's controls are so sensitive that a slight overturn can send it spinning out of control, resulting in a crash. The sequence isn't even very long, but that doesn't save it from being one of the franchise's absolute worst.

5 The Erymanthian Boar (Assassin's Creed: Odyssey)

Assassin's Creed Odyssey The Erymanthian Boar

As the franchise has moved away from the more "grounded" nature of its earlier entries, even the worst missions have become a lot less painful. It's been a mostly welcome change. However, one mission that still manages to be infuriating is the killing of the Erymanthian boar.

This enemy is a brutal combination of issues: she shows up early in the game, and she has a massive health pool. That means it takes a really long time to whittle away the boar's health bar. The frustration doesn't stop there though. Worst of all are the Erymanthian boar's "farts." There's no other way to describe them: clouds of poisonous gas that she leaves in her wake. All these factors combine to make her one of the hardest fights in the whole game.

4 Hell On Wheels (Assassin's Creed: Brotherhood)

Assassin's Creed Brotherhood Hell On Wheels

Franchise fans likely know this mission simply as "The Tank Mission." That's because it involves Ezio stealing a tank and driving it through a gauntlet of cannons and other tanks.

The tank moves painfully slowly, that's issue number one. Issue number two: in order to get 100% synchronization on this mission, the player has to drive this tank at a snail's pace through that gauntlet without getting hit. Needless to say, that's virtually impossible. The "chef's kiss" of frustration is that, should the player fail the mission, they go all the way back to the very beginning (before Ezio has even stolen the tank) because this mission has no checkpoints.

3 The Midnight Ride (Assassin's Creed 3)

Assassin's Creed III The Midnight Ride

There are at least a dozen missions in Assassin's Creed 3 that are annoying, but only a couple that are truly frustrating. The first is this mission, where Connor travels with Paul Revere on his famous "The British are coming!" ride across the Frontier. This should be an exciting, epic sequence, right?

Wrong. Much like when Ezio was tasked with moving a chest of money across Rome, Connor must travel via directions dictated to him by Revere. Go the wrong direction, Revere will call the player an idiot. To make matters worse, Revere can actually get lost. What does the player do then? Just...wander around. Eventually, Revere gets his bearings. It's a wonder how this mission even made it into the game.

2 Flying Machine 2.0 (Assassin's Creed: Brotherhood)

Assassin's Creed Brotherhood Flying Machine 2.0

Ezio is, once again, getting looped into some nonsense by Leonardo da Vinci. This time, he needs to steal a flying machine from the Templars, use it to destroy some towers, and then chase down a messenger on a horse. What's so bad about that?

RELATED: Saddest Scenes in Assassin's Creed

For one, 100% sync requires players to not be hit or seen by enemies during the whole sequence. It's annoying but doable. The real travesty is that the flying machine is actually more of a "falling-with-style" machine. In order to gain altitude, Ezio must start bonfires on the ground using the machine's bombs, then fly above them to float back into the air. Meanwhile, the messenger's horse just gets to run in a straight line. He almost always gets away, so, good luck.

1 The Giant And The Storm (Assassin's Creed 3)

Assassin's Creed III The Giant And The Storm

The worst mission on this list has just one objective: sink three ships by igniting their power kegs. Where does it go wrong? For one, igniting powder kegs is a finicky endeavor given the imprecise aiming of the cannons on Connor's ship. But it gets so much worse.

Even a direct hit doesn't guarantee the powder kegs will ignite, it just gives them a chance to do so. Already at the whim of the game's RNG, players then get to deal with the fact that there are only three ships to destroy in the whole mission, meaning if one sinks without its power keg igniting (and instead due to, say, cannon fire), it requires restarting the mission. An objective that relies on random chance for success, with no room for error, is just insulting.

MORE: Fan-Made Assassin's Creed Infinity Video Imagines a Persian Setting Using Unreal Engine 5