Throughout Adventure Time, there was always some danger lurking around the corner for the heroes Finn and Jake to vanquish. That said, the villains in question varied in terms of the threat level posed. Some were small nuisances that were quickly taken care of, while others were nearly unstoppable foes the duo wasn't always prepared for.

The most dangerous Adventure Time villains have pushed Finn and Jake farther than ever before. Many of these antagonists even defeat Finn and/or Jake, leaving the hero to work to save one of their friends. However, there were plenty of times when the duo found their own way, even if the missions were extremely difficult.

Updated by Ajay Aravind on November 17, 2023: Adventure Time is arguably one of the most popular animated shows ever, as evidenced by the overwhelming scope of the franchise. The series has spawned two others, subtitled Distant Lands and Fionna and Cake, both of which received critical acclaim. Given that there are numerous enemies to antagonize Jake and Finn, however, we've updated this list containing the most dangerous Adventure Time villains.

10 Maja Had an Almost Fool-Proof Plan To Destroy the Candy Kingdom

She Summons Darren The Ancient Sleeper

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When Marceline's boyfriend at the time, Ash, sells her prized teddy bear to Maja, she and Princess Bubblegum set out to retrieve it. PB winds up face-to-face with Maja and trades the toy with one of her prized possessions. The emotional magic emanating from PB's T-shirt, a gift from Marceline, helps Maja summon Darren The Ancient Sleeper to destroy the Candy Kingdom.

With the kingdom's forces outmatched, it's up to Finn and Jake to save the day. Luckily for them, they were already acquainted with another cosmic being, the Ancient Psychic Tandem War Elephant. The APTWE turned out to be one of the few beings in Adventure Time who could defeat Maja's deadly summon.

9 Ricardio's Brilliant Plans Were Only Defeated Because of Finn's Paranoia and PB's Strength

Ricardio Originally Appeared To Be a Nice Guy and Suave Gentleman

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When first introduced in Season 1, Ricardio appeared to be a nice guy. He was a suave gentleman who seemed to have great chemistry with Princess Bubblegum, which drove Finn to jealousy. Even Jake saw nothing wrong with him but supported Finn in spying on the heart-shaped man. After the two spoke to a beaten-down Ice King, they learned that Ricardio was the Ice King's heart and had gained its own sentience after an experiment went haywire.

Ricardio's original plan was to rip out PB's heart and marry it, but that plan is foiled by Finn and Jake. The villain then returned with oversized limbs attached to his heart-body and vowed to marry PB as a whole, not just her heart. After kidnapping Finn and Jake, PB agreed to marry him if he could best her in combat. She proceeded to destroy Ricardio's new body, saving the heroes.

8 Goliad Had Only One Rival To Fend Against His Psychic Powers

Stormo and Goliad Are Evenly Matched in an Eternal Psychic Battle

After Princess Bubblegum was nearly killed by the Lich, she worried that if she were to die at any point, her kingdom would fall to ruin under the wrong leadership. She created the being Goliad to take her place. However, when she assigns Finn and Jake to show Goliad the ropes of leadership, they all quickly realize that Goliad is not fit for the job.

Goliad turned against PB's rule, believing they had to use their psychic powers to control the candy people. Finn and Jake were no match for Goliad, so PB used what little time she had to create another psychic being called Stormo. Since Stormo has Finn's DNA, he is heroic and stands to fight for the Candy Kingdom. The two beings are evenly matched in a psychic battle that PB says will last for eternity.

7 The Guardian Protected the Island of Humans Against One of Their Own

This Robot Is Programmed To Destroy Anyone Who Comes Near the Island's Shoreline

When Finn learned that there were humans alive aside from him and Susan Strong, he, Susan, Jake, and BMO traveled to the islands where they resided. What they weren't prepared for was the giant protector of the humans that lived there. This enemy was a huge robot called Guardian, who was programmed to destroy any beings that entered the waters near the island's shoreline.

The Guardian has prevented humans from leaving the islands for decades and was part of the reason Finn was separated from his parents. The heroes were startled by their first encounter with Guardian and were nearly drowned by its attack. Since it was designed to be an impenetrable force, the only way to stop its might was to change its programming. After meeting Finn's mother's consciousness, the heroes uploaded her mental commands directly to the Guardian's mind to make it stop.

6 The Empress Would Have Killed Finn If It Weren't for Princess Bubblegum

The Empress Fails To Hypnotize the Ice King Due to His Iconic Inanity

After Princess Bubblegum helped Marceline to become mortal, powerful vampires from Marceline's past were unleashed. One of them was The Empress, who used the Ice King to capture Marceline and Finn. The Empress wanted revenge and to ensure that Marceline wouldn't get in her way again. As for Finn, he was wanted for his human blood.

The Empress thought she had the Ice King under her spell, but since he's "too thick" to be hypnotized, it never worked in the first place — he was just following her because he's obsessed with women. Both Finn and Marceline struggled in their fight against The Empress when Princess Bubblegum arrived to stun her with her latest invention. This gave Marceline the chance to stake The Empress, saving her and Finn's life.

5 The Moon Was a Terrifying Threat for Finn and Jake

Marceline Barely Manages To Suck in the Moon's Soul

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After Marceline is poisoned in the battle against the vampires, the heroes' only hope to save her life is a vampire enemy called the Moon. The Moon has incredible healing powers that prevent her from being wounded in any way. Princess Bubblegum rushes Marceline to her lab in the Candy Kingdom and leaves Finn and Jake the task of taking the Moon to Marceline so she can suck her soul and take her healing.

Finn and Jake are then chased down by the horrific night creature. Although they succeed in bringing her to Marceline, they fail to hold back the Moon. Luckily, Marceline is just conscious enough to suck in the Moon's soul and save herself with the healing ability.

4 Fern Was a Daunting Threat Toward the End of the Series

Fern Eventually Accepts Death and Destroys His Demon Version

Fern is created after Finn breaks the Finn sword, which reflects Finn's likeness, with the magical grass sword. The small Finn reflected in the Finn Sword was cocooned by the Grass Demon, and after some time, Fern came to be. Throughout his time in the series, Fern is very conflicted about his identity, many times battling with Finn to take his place. Fern inevitably joins Uncle Gumbald's war against Princess Bubblegum.

As his knight, he is strong enough to defeat Finn, who has to be rescued by the character Aunt Lolly. At the end of the series, Finn sees that the Grass Demon has been torturing Fern since he was first created, but without the Demon Fern, he won't have a physical body. Fern ultimately accepts death and destroys the demon, freeing himself at last.

3 Gunter Wound Up Becoming the Biggest Unforeseen Threat

Gunter Regains His Memories as Orgalorg, Breaker of Worlds

It's revealed that Gunter is a monstrous entity named Orgalorg, who had once tried to destroy the world centuries ago. They were turned into their iconic penguin form and had their memories erased by Grod Gob Glob Gob. After the powerful being was destroyed, Orgalorg's memories finally returned.

The recurring vision of a comet was what Orgalorg was waiting for to give them power. In their true form, the cosmic being makes it to the comet when Finn launches himself into Orgalorg's mouth, cutting them up from the inside. It was one of the closest calls for the heroes, but they managed to turn the heinous villain back into their cuddlier form: Gunter the Penguin.

2 The Lich Has Always Been Finn and Jake's Greatest Enemy

The Lich Exists Solely for the Sake of Destroying All Living Things

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Unlike most villains in Adventure Time, the Lich exists solely for the sake of destroying all living things, not because it craves power or destruction, but merely because that's why it exists in the first place. The villain has overwhelming magical power and strength that have proven to be extremely troublesome for the heroes.

Aside from offensive magic, the Lich can control the mind and possess others, as well as raise an army of the dead and kill anything it touches. No matter how many times the heroes have overcome this villain's might, this horrifying villain always comes back. One time, the Lich's return resulted in an entire civilization being led to ruin.

1 GOLB Is Even Stronger Than the Lich

GOLB Is a Pure Manifestation of Chaos and the Series' Final Antagonist

Arguably the most powerful Aventure Time character, GOLB is mentioned in name throughout the series. In the end, King Man, Betty, and Maja bring him to Ooo, unaware of how overwhelming he would be to handle. As a pure manifestation of chaos, GOLB is able to turn any beings into chaotic monsters. Once he swallows a living being whole, they cannot be brought back by any means of magic.

The Cartoon Network series' final antagonist was so devastating to the heroes that it looked as though there was no escape from death. Finn, Ice King, and Betty are trapped inside the being's stomach, preparing for their demise when they realize that singing in harmony is GOLB's singular weakness. As a last resort, they all harmonize and quell the satanic beast.