The success of the Final Fantasy series can in large be put down to its fantastic cast of characters. While the gameplay certainly does a wonderful job of engaging players and the story a fine job of entertaining them, without these wonderful heroes and villains, the games just wouldn't be anywhere near as enjoyable.
While the series' antagonists can often be incredibly similar, there's quite a bit of variety when it comes to the villains. Some are humans who have been driven to madness while others are monsters and demons from distant worlds. One thing that they all have in common, however, is that they are incredibly intimidating. Some are definitely a lot more fearsome than others though.
10 Seifer (Final Fantasy VIII)
Throughout the series, summons (or Guardian Forces as they're known in Final Fantasy VIII) have been portrayed as all-powerful beings with abilities far beyond those of mere mortals. Even in games where they can technically be defeated, they never actually die. It's for this reason that Seifer killing Odin came as such a huge shock.
There have been plenty of occasions throughout the series where villains have murdered NPCs or party members, but never before had one been able to kill a summon. That Seifer was able to do so and the manner in which he did it elevated him from a run of the mill villain to one who was seemingly capable of anything.
9 Exdeath (Final Fantasy V)
While Exdeath's initial design might not be the most frightening, his raw power and attitude more than makes up for it. The way that he's able to swat the party aside is certainly impressive, but it's his assertion that they are not even worth killing due to how weak they are that really drives home the magnitude of his true strength.
Exdeath shows no empathy whatsoever and struggles to understand any emotions other than hate or anger. There are moments when this anger is unleashed on the party directly, but others where he instead wields it against his own forces. It's perhaps not until he kills Galuf though that players realize just how dangerous Exdeath really is. By the time he reveals his final form, there can be absolutely no doubt.
8 Hojo (Final Fantasy VII)
Although he does play a fairly significant role in the events of Final Fantasy VII, Hojo's actions prior to the game have a far greater influence on the game's story. When players are first introduced to him, he comes across as little more than a mad scientist. The more that players learn about Hojo's past though, the more intimidating he becomes.
Hojo's obsession with the promised land and the ancients has corrupted what was once a brilliant mind. He's now incredibly unpredictable and capable of just about anything. The way Hojo torments Aerith by talking about the death of her mother is demonstrative of just how unhinged he has become, and he takes this a step further when he decides to experiment on himself. By doing so, Hojo ensures that his outward appearance becomes every bit as frightening as what is on the inside.
7 Barthandelus (Final Fantasy XIII)
The power that Galenth Dysley wields from his throne in Sanctum makes him a fearsome opponent right off the bat. He has the might of a nation at his back and spies everywhere. That he's been using this power to pull the party's strings comes as an unexpected revelation, but nowhere near as shocking as when he is revealed to be a fal'Cie.
Galenth's true form, Barthandelus, is monstrous both in terms of size and appearance. He has the power to back this up and, knowing what is at stake should the party fail to defeat him, there's every reason for the party to be afraid. While incredible power is a common trait in Final Fantasy villains, it's rare that they are able to back this up with the political capital that Barthandelus possesses.
6 Chaos (Final Fantasy)
The original villain of the series, Chaos' intimidation comes largely from his design. While demons have become commonplace in video games in the years since Final Fantasy's release, in 1987 this depiction was really quite frightening. That's not all that was scary about Chaos either.
His powers in combat are incredible, but, compared to his ability to manipulate time, they are nothing. While the party does eventually grow strong enough to beat Chaos in battle, the loop that Garland creates ensures that they can never truly defeat him. The idea that the heroes are destined to repeat their journey for all of time is a harrowing one.
5 Sin (Final Fantasy X)
Sin's presence is felt right from the beginning of Final Fantasy X and the more that players learn about it, the more terrifying it becomes. That Sin can only be delayed rather than fully defeated makes the death and destruction it brings seem inevitable and these are things that the beast can dish out incredibly effectively.
Sin's destructive powers make it a frightening foe and its sheer size makes defeating it feel like an impossible task. Although players do eventually figure out a way to stop Sin for good, for the vast majority of the game it is an ever-present threat. Knowing that it could appear anywhere and at any time really helps to keep the player on the edge of their seat.
4 Zemus (Final Fantasy IV)
Some of the antagonists from the earlier Final Fantasy games are fairly forgettable, but Zemus isn't one of them. Even in his Lunarian form, the way that he towers over the party makes defeating him seem an incredibly daunting task. His psychic powers make him nigh-on invincible and his complete disregard for humanity further highlights the threat that he poses.
As with some of the series' other villains, Zemus takes on another form after his initial defeat. His spirit form, Zeromus, is absolutely terrifying thanks in large to its wonderful design. It does a fine job of capturing the pure evil that was hidden beneath Zemus' outer shell and provides players with yet another seemingly insurmountable challenge.
3 Ultimecia (Final Fantasy VIII)
How exactly can one defeat a villain that's able to manipulate time and can bewitch some of the most powerful people on the planet? That's the question that a lot of players were asking themselves upon Ultimecia's reveal in Final Fantasy VIII. Her horn-like hairdo and black feathered wings are straight from a catwalk in hell and her tyrannous disregard for life makes her a truly frightening force.
It's not just Ultimecia's actions that make her terrifying, but also her intentions. During her inauguration speech, she mocks the people of Deling and promises to bring forth a new reign of terror. This promise, when combined with the knowledge that there is nobody who can stop her, makes Ultimecia terrifying not only in the present but also the future.
2 Sephiroth (Final Fantasy VII)
Square Enix got a lot of things right when remaking Final Fantasy VII, but their implementation of Sephiroth wasn't one of them. One of the things that made him so intimidating during the original game was that players saw only the carnage that he left in his wake during the game's early stages. The blood-splattered corridors of the Shinra building were a shocking sight to behold and painted a picture of a true monster. This helped to make his eventual reveal all the more impressive.
Everything about Sephiroth is unnerving, from his cold stare to his enormous blade. That he's able to use his connection with Cloud to show up literally anywhere is scary enough, but that Sephiroth can also control the protagonist's actions is beyond terrifying. Not only does Sephiroth use this connection to obtain the Black Materia, but there's also a moment when he tries to make Cloud kill Aerith. After his attempt fails, Sephiroth simply falls from the sky and does it himself.
1 Kefka (Final Fantasy VI)
Many of the villains in Final Fantasy are intimidating because of the power that they wield, but Kefka is a little different. He's certainly powerful, but it's his complete and utter disregard for all life that really sets him apart. The way that he is willing to strike down his allies without a second thought perfectly demonstrates this, as too does the destruction that he unleashes on the planet.
When it comes to body counts, few can compare to Kefka. It's never stated just how many are killed during the cataclysm, but, judging from the aftermath, one suspects it's in the millions. All of this is backed up by his wonderful design. Kefka wears his insanity on his face like a badge of honor, while his maniacal laugh and the aptly named track "Dancing Mad" that plays during the final showdown serve as the finishing touches to a wonderful villain.