Resident Evil may not have invented the survival-horror genre, but it is without question the most successful horror franchise in gaming history. Since it debuted in the mid-90s, Resident Evil has seen countless sequels, spinoffs, novels, film adaptations, and more, giving fans of the franchise no shortage of bone-chilling content to enjoy.

When one considers the sheer number of Resident Evil games that have been released, it's no surprise that the franchise has produced a ton of freaky monsters to haunt players' nightmares over the years. Out of all the Resident Evil monsters, though, the following 20 stand out as especially creepy.

20 1. Brain Sucker/Drain Deimos

While they're not exactly the same creatures, Brain Suckers and Drain Deimos are both the result of arthropods becoming infected with the T-Virus. Appearing in Resident Evil 3: Nemesis, these horrific-looking creatures are like giant fleas, pouncing on their victims and sucking the blood from their body. While they may not be the most famous monsters the series has produced, they're definitely some of the ugliest.

19 2. Cerberus

Resident Evil: Scariest Moments in Series History - Zombie dog jumps through window

The Resident Evil franchise is filled with zombie dogs of all types, but the most recognizable are the dobermans that the Umbrella Corporation transformed into monsters as part of the Cerberus project. In the first Resident Evil game, these disfigured monsters murder Joseph Frost, and chase the rest of the S.T.A.R.S. Alpha team into the mansion, where they end up facing off against even greater horrors. The first time players encounter a Cerberus in-game occurs shortly after the start when one bursts through a hallway window in a scene that we named one of Resident Evil's scariest moments.

18 3. Chainsaw Man

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Resident Evil 4 may be the highest-rated game in the series, but it has also been criticized by some fans for straying too far from the franchise's horror roots. However, that doesn't mean it lacks scary monsters, and in fact, Resident Evil 4 is home to some of the scariest monsters in the entire series. One of the most memorable is the burlap sack-wearing Chainsaw Man, who is capable of decapitating protagonist Leon S. Kennedy with ease, and whose revving chainsaw is enough to strike fear in the hearts of even the bravest gamers.

17 4. Chimera

To create the Chimeras, Umbrella kidnapped homeless women and impregnated them with an embryo comprised of both human and fly DNA. The result is an absolutely grotesque creature not unlike Jeff Goldblum from the classic body horror movie The Fly. Luckily, most of the Chimeras were destroyed in the mansion explosion at the end of the first Resident Evil, but they have still managed to pop in other games in the series over the years.

16 5. Comms Officer/Scagdead

resident evil revelations comms officer

The unfortunate Comms Officer in Resident Evil: Revelations was transformed into a ghastly monster known as a Scagdead thanks to the T-Abyss virus. A strange, two-headed, bulky creature, the build-up and initial encounter with this enemy stands as one of the most effective parts of Revelations.

15 6. Crimson Heads/Zombies

Resident Evil: Scariest Moments in Series History - Crimson Head

The classic zombie deserves a spot on this list, especially considering the creepy first encounter players have with them in the original Resident Evil game. The sight of a zombie munching on a dead S.T.A.R.S. member only to slowly turn its head around and eyeball the player is undoubtedly one of the most iconic moments in horror gaming history. However, the Resident Evil remake on the GameCube somehow found a way to make the mansion's zombies even scarier.

Enter the Crimson Heads. In the Resident Evil remake, players have to burn zombies' bodies after killing them or else they may evolve into faster, clawed creatures called the Crimson Heads. Since players have limited inventory space, they have to decide between carrying around the supplies to burn any zombies they happen to kill, or running the risk of having a mansion full of these nearly unstoppable monsters.

14 7. Eveline

Resident Evil 7's Ending Explained - Eveline

Considered the next generation of bio-weaponry, Eveline was created to be a devastating force on the battlefield. Taking the form of a seemingly harmless little girl, Eveline is capable of mind control and morphing people into blob-like creatures called Molded. Eveline's true form is a mess of grey flesh and black mold, and it's a disturbing sight to behold.

13 8. G (William Birkin)

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One of Umbrella's key scientists and the man behind many of the company's terrible experiments, William Birkin winds up infected with the G-Virus, turning into a constantly-evolving monster named G. He begins hunting down his daughter, Sherry Birkin, and causes the citizens of Raccoon City to become infected with the T-Virus, turning many of them into bloodthirsty zombies. G's creepy appearance alone earns him a spot on this list, but his importance to the franchise's lore is also notable.

As it turns out, G will be making a comeback to the franchise as part of the Resident Evil 2 remake, and we've already seen him do battle with Claire Redfield in various gameplay trailers released for the upcoming game.

12 9. Hunters

Resident Evil: Scariest Moments in Series History - Hunter and Chris Redfield

One of Umbrella's most successful bio-weapons is the Hunter, a species created by combining reptiles, humans, and the T-Virus. In the video games, Hunters are some of the deadliest creatures players can come across, capable of one-hit kills through graphic decapitation. Far smarter than run of the mill zombies and most of the other monsters on this list, it's no surprise other bio-weapon corporations have continued to produce their own Hunters since Umbrella's demise.

11 10. Jack Baker

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"Welcome to the family, son!" The patriarch of the Baker family, Jack Baker is a surprisingly tragic character in Resident Evil 7. Under the control of Eveline, Jack becomes a virtually indestructible monster who stops at nothing in his quest to murder Ethan Winters.

Over the course of the game, Jack is mutilated, shot numerous times, and even lit on fire, but nothing seems to slow him down. Eventually, Jack mutates into a huge Molded creature, but his human form that taunts and stalks Ethan throughout the plantation is arguably far scarier.

10 11. Iron Maiden/Regenerator

Gaming's 10 Most Terrifying Monsters - Resident Evil 4 Regenerator

One of gaming's scariest monsters is without a doubt the Regenerators from Resident Evil 4. The Regenerators are basically invincible unless the Plagas parasites crawling underneath their skin are attacked directly, requiring Leon to collect a special infrared scope to take them out. Meanwhile, Iron Maidens are an even deadlier take on the Regenerators, filled with more parasites and capable of producing spikes from their fleshy bodies.

9 12. Leech Zombie

In Resident Evil 0, Rebecca Chambers and Billy Coen encounter a number of Leech Zombies, which are regular zombies covered in leeches infected with the T-Virus. Leech Zombies are smarter than the average zombie, and the mass amount of leeches provide a sort of armor for their host, making them even more difficult to kill. The disgusting, slime-covered leeches really increase the gross-out factor for these monsters as they crawl all over each other and their host's undead flesh.

8 13. Lickers

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Besides the franchise's standard zombies, some of the most recognizable monsters in Resident Evil history are the Lickers that were first introduced in Resident Evil 2. Lickers are notable for their skinless bodies, sharp claws, fanged teeth, exposed brains, ability to crawl on walls and ceilings, and of course, their signature long tongues. The first encounter with a Licker in Resident Evil 2 is one of that game's most startling scenes, and it will be interesting to see if the upcoming Resident Evil 2 remake can do it justice.

7 14. Lisa Trevor

Resident Evil: Scariest Moments in Series History - Lisa Trevor and Chris Redfield

The Resident Evil remake on the GameCube introduced some new monsters that weren't in the original game, like the aforementioned Crimson Heads and the downright disturbing Lisa Trevor. The daughter of the architect that built the mansion, she was abducted, abused, and tortured for years as she was used as a test subject for Umbrella's evil experiments.

The experiments transformed her into a horrible, hulking beast that was nearly invincible, with players encountering her out in the dark woods surrounding the mansion as well as the complex cave system beneath the estate. Lisa's backstory and her twisted appearance make her not just one of the creepiest monsters in Resident Evil history, but also one of the most tragic.

6 15. Marguerite Baker

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Once a loving wife and mother, Marguerite Baker has warped into a truly sick and twisted monster thanks to the powers of Eveline during the events of Resident Evil 7. On top of the usual deformities that come with being under Eveline's spell, Marguerite also moves her family toward cannibalism, making meals for them comprised largely of human remains. She has also managed to develop the ability to control a variety of insects, making her one of the creepiest members of the Baker family by far.

5 16. Mia Winters

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Mia Winters is the missing wife of protagonist Ethan Winters in Resident Evil 7, but when Ethan finds her at the Baker family plantation, she isn't exactly human anymore. Possessing incredible strength and prone to sudden fits of rage, Mia winds up cutting off her own husband's hand with a chainsaw within moments of their reunion. Like the other Baker family members, Mia is as tragic as she is horrifying, which makes her far more interesting than many other Resident Evil franchise monsters.

4 17. Nemesis/Tyrant

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After Capcom releases the Resident Evil 2 remake in January, many fans are keeping their fingers crossed that it remakes Resident Evil 3: Nemesis next. Part of the reason why Resident Evil 3 is so popular is due to the monster that it's named after, the ugly Tyrant known as Nemesis, which unlike similar creatures, is actually capable of some intelligent thought. Dressed in a leather suit and armed with a rocket launcher, Nemesis relentlessly pursues Jill Valentine through the zombie-infested streets of Raccoon City, hoping to fulfill its singular goal of killing every S.T.A.R.S. member. Nemesis's tendency to randomly burst through walls gives him a distinct level of unpredictability not many Resident Evil baddies possess, and his unique look has helped him become one of the franchise's most iconic monsters.

There have been other memorable Tyrants in the Resident Evil series besides Nemesis, though. The first Tyrant players fight at the end of the original Resident Evil comes to mind, as does the yellow Bandersnatch Tyrant from Code: Veronica. There's also Mr. X, the towering Tyrant from Resident Evil 2 that stalks Leon in that game and is making a comeback in the Resident Evil 2 remake.

3 18. Rachel Foley

resident evil revelations rachel foley

During the events of Resident Evil: Revelations, Rachel Foley is sent to the Queen Zenobia ship on a mission she wanted no part of, and winds up infected with the T-Abyss virus for her troubles. The virus warps Foley into a special version of the Ooze monsters that had taken over the ship, complete with a large claw not unlike the Crimson Heads. The Ooze monsters themselves may not have left much of a lasting impression on Resident Evil fans, but the Ooze form of Rachel Foley is likely an image many are struggling to get out of their head.

2 19. Revenant

resident evil revelations 2 revenant

In Resident Evil: Revelations 2, players encounter Revenants, which are deformed monsters that are made up of flesh and various torture instruments. Combining their bodies with saws and nails gives them an especially creepy look, and they are definitely the standout monsters from Revelations 2.

1 20. U-3

Most of Resident Evil 4's boss fights focus on action over horror, and while that is still true for U-3, its visual design alone earns it a spot on this list. A horrible hybrid of giant insects and an unfortunate human being, the U-3 is hauntingly referred to as "It" before it makes its grand entrance as part of one of Resident Evil 4's most startling jump scares. The U-3 is the stuff of nightmares, and is most certainly one of the creepiest monsters in series history.