Throughout the nearly four-decade tenure of Nintendo's Metroid franchise, protagonist Samus Aran has grappled with dozens of different foes. Specifically, the franchise's titles are well-known for their unique boss fights. Even more memorable than the fights themselves, some bosses are iconic due to their status within Metroid's lore and their relation to Samus in particular.
2021's Metroid Dread expanded upon the series' mythos even further, finally delivering a sequel to 2002's Metroid Fusion, which had been the story's latest entry for decades. Dread saw the return of quite a few faces while unraveling long-standing mysteries about the game's universe, and its commercial success is a testament to this alongside the game's intense gameplay and addicting exploration. Thanks to Dread's release, Metroid's story is moving forward after decades of prequels and remakes.
Since the successor to Metroid Dread likely won't be arriving for some time, it's a great opportunity to look back at the most influential bosses in the franchise.
7. Metroid Prime (Metroid Prime)
As seen in titles such as Metroid II: Return of Samus and its remake Metroid: Samus Returns, the titular Metroid creatures are capable of metamorphosing and achieving various forms across their life cycle. However, only the enigmatic Chozo race could have foretold the coming of a creature that surpassed any other Metroid. On their adopted world of Tallon IV, the Chozo held a prophecy of a creature known as the "Worm." This creature was expected to spell impending doom for the entire planet, and that's exactly what it did. A living meteor known as a Leviathan crashed into the surface of Tallon IV from the planet Phaaze, releasing the volatile mutagen Phazon onto the planet and mutating a lone Metroid into the awaiting beast.
Although the Chozo tried to seal away the corrupting Phazon, they only succeeded in slowing it down. As the Chozo on Tallon IV died out, they left behind modules for a Chozo Power Suit, hoping their race's eventual champion would find them and save the planet. The presence of Phazon drew the attention of the Space Pirates years later, leading Samus to follow them.
After collecting the upgrades, Samus faced off against the Worm, which had come to be known as Metroid Prime. Compared to all other Metroids the bounty hunter faced during her travels, Prime was likely the most dangerous and imposing of them all. Not even the Omega and Queen Metroids could hold a candle to Prime's vicious mutations. Furthermore, although Samus defeated Prime's original form, the creature would live on. By absorbing portions of Samus' Phazon Suit, Prime would be reborn as Dark Samus, an even deadlier enemy.
6. SA-X (Metroid Fusion)
After the events of Metroid II, Samus had seemingly succeeded at destroying every known Metroid in the galaxy, save for an infant that had taken a liking to her. This baby Metroid was handed over to the Galactic Federation, and the galaxy was seemingly at peace. Unfortunately, the Metroids' natural food source, the X Parasites, soon reproduced and overwhelmed the Metroid home planet of SR388. After returning to the planet to protect a biological research team, Samus killed a creature that an X Parasite was mimicking, causing the X to infect her. This infection soon led to her losing consciousness, crashing her ship, and being retrieved by a Galactic Federation medical team.
Samus' Power Suit had become so infected by the X that the suit's biological components were fused to her body. Doctors had to surgically remove massive portions of her suit and quarantine them on a nearby research station. However, this surgery wasn't enough, and Samus still nearly died. Fortunately, the baby Metroid's cells were used to create a vaccine that saved Samus' life, albeit changing her DNA and making her part Metroid.
Back on the research station, the X, who are capable of mimicking their infected prey, used the portions of Samus' Power Suit to create a copy of her at her full strength. This creature, dubbed the "SA-X," wreaked havoc throughout the station and hunted the weakened Samus as she investigated its mayhem.
Although this Samus doppelgänger wouldn't be the last of its kind, it was the first to appear. It remained an impossible boss to defeat in Metroid Fusion until the game's final act. Unlike many other Metroid games, players had to utilize stealth and escape tactics to avoid the SA-X instead of fighting it, as it could kill Samus effortlessly. Its moment in the spotlight was short, but there's no question that the SA-X was one of Samus' most terrifying encounters.
5. Dark Samus (Metroid Prime 2-3)
The other doppelgänger of Samus proved to be a completely different animal. A being blended of pure Phazon, Samus' Phazon Suit, and the remains of Metroid Prime, Dark Samus proved to be highly intelligent and dangerous. Following Samus' battles against the Space Pirates on multiple planets, Dark Samus killed all in her way in order to destroy her original, utilizing weapons similar to Samus but also by absorbing and manipulating amounts of Phazon that would kill any other life form.
Dark Samus' personality began unstable, with it cackling maniacally and struggling to keep a hold of its psyche. By Metroid Prime 3, the antagonist became much calmer and even brainwashed Space Pirates and ordered them into battle. Capable of long-term strategizing due to its increased intelligence, Dark Samus became an iconic foil to Samus throughout the Metroid Prime series, matching her pound-for-pound in smarts and instincts.
4. Kraid (Various)
A titanic reptilian creature Samus first encountered in the original Metroid, Kraid is a well-renowned member of the Space Pirates and is often found on planets the pirates occupy alongside Ridley. In the games that he appears in, he is almost always required for Samus to defeat before entering the Space Pirate stronghold. His breathtaking size has always given Samus plenty of trouble, and being capable of firing chitinous spikes from his stomach doesn't make things any easier.
Although much of Kraid's story and lore is piecemeal at best from old comic books and manuals, his recurrence throughout the series as a brutish and imposing boss has placed him squarely in the pantheon of Metroid villains. His canceled appearance in Metroid Prime stung, but Metroid Dread brought him back in spectacular fashion. Try as she may, Samus just can't shake this lumbering boss.
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3. Mother Brain (Various)
Originally created by the Chozo, Mother Brain served her purpose as an AI until she saw a chance to turn against her creators. When the Space Pirates attacked the Chozo world of Zebes, Mother Brain assisted the pirates' extermination of the Chozo. A young Samus, who was under the Chozo's care after losing her human family, was in disbelief that the Chozo's greatest asset had become a major factor in their destruction. Mother Brain even attempted to coax Samus into joining the Space Pirates, but the young hunter refused.
Mother Brain's intelligence quickly made her superiority evident, and she became the leader of the Space Pirates despite being limited physically. Though Mother Brain was defeated in the original Metroid, her body was reconstructed in Super Metroid, which included a second form that saw her become a near-indestructible monster. Were it not for the baby Metroid saving Samus by bestowing her the Hyper Beam as it died, she likely would have fallen to the pirate leader.
Mother Brain would return again in Metroid: Other M in the body of an android intended to control bio-weapons for the Federation. However, the android began to develop Mother Brain's ruthless personality and used the creatures to attack a station known as the Bottle Ship. Thanks to an act of sacrifice by Samus' ex-commander in the Federation military, Adam Malkovich, Mother Brain detonated alongside an entire segment of the Bottle Ship, seemingly destroying her permanently.
Mother Brain has spent some time on the sidelines in subsequent titles, but there's no doubt she is one of the perpetual thorns in Samus' side, orchestrating the Space Pirates to continue to terrorize the galaxy despite the bounty hunter's best efforts.
2. Raven Beak (Metroid Dread)
A new boss with an insidious past, Raven Beak is a Chozo leader of the Mawkin tribe. Although Chozo throughout Metroid's media are often portrayed as kind and benevolent, Raven Beak is anything but. First being referenced in Metroid: Samus Returns' "Chozo Files," it is revealed that Raven Beak set the events into motion that led to the series' main story. The files reveal that another tribe of Chozo, the Thoha, engineered and controlled the Metroids to exterminate the X Parasite scourge from the planet SR388. Though they were initially successful, the Metroids began evolving and grew too powerful for their masters. In a bid to save the galaxy, the Thoha asked Raven Beak and his Mawkin to help seal the Metroids within the planet.
Raven Beak acquiesced but had a change of heart when the Thoha stated they planned to blow up SR388. Seeing the Metroids as weapons that could be used to impose "order" on the galaxy, Raven Beak murdered the Thoha leaders, leaving the Metroids on SR388 for the Space Pirates to find and inadvertently release on the galaxy.
In Metroid Dread, Raven Beak faces Samus early and nearly kills her, sparing her life only due to his knowledge that Samus' Metroid DNA makes her the last living Metroid in existence. Monitoring her on the planet ZDR, Raven planned to let Samus develop her Metroid abilities to their peak before stealing her genetic material and creating an army in her image that he could control. He also reveals to Samus that the Chozo DNA she inherited to use the Power Suit was partially his, mockingly referring to her as his daughter.
Even as Samus grew in power, she still couldn't overcome Raven Beak. He overpowered her once more, leaving her moments from death. In an act of desperation and rage, Samus' Metroid DNA fully expresses itself, transforming her into a Metroid hybrid and providing her another Hyper Beam that allowed her to finally prevail.
Although Raven has only appeared for a short while, his status as the puppet master that put nearly all of Metroid into motion sees him skyrocketing in his status as a villain.
1. Ridley (Various)
Arguably the reason Samus Aran is who she is and why she has a burning hatred for the Space Pirates, Ridley is the bounty hunter's arch enemy and recurs as a boss in nearly every title in the franchise in some form. Although he is only the final boss in Metroid: Samus Returns, his ties to the protagonist run deep and his effect on her psyche is substantial, but why is that the case?
On the colony K-2L, three-year-old Samus Aran lived with her parents in peaceful bliss. As a general of the Space Pirates, Ridley led a raid on the colony that led to the extermination of every human on the planet, save for Samus. Killing her mother in front of her and leading her father to sacrifice himself out of desperation, Ridley left Samus to die alone. Her fate was only reversed by the intervention of the Chozo, who took Samus in and trained her to become a warrior. Since then, Samus has battled Ridley in a majority of the franchise's titles, returning in different forms and hounding the hunter again and again.
Ridley's near-constant presence is a reminder to Samus of what she lost and how she became who she is. Although he's her greatest enemy, Samus likely never would have become the galaxy's greatest protector if it wasn't for Ridley's sadistic blood thirst. The two are essentially tied together at the hip, battling each other again and again until one is gone for good. Several bosses have left a mark on Samus as a protagonist, but Ridley set the bar.