Over the long history of the Pokémon anime, Ash has faced some truly devious enemies who've posed a serious threat, not only to Ash, but in some cases to the entire world. Some of these foes were even capable of wielding the tremendous power of Legendary Pokémon, making them truly dangerous to stand against.

The strongest villains often aren't working alone; they'll have entire evil teams operating under their command, able to outmaneuver the heroes with sheer numbers, if not strength. They're often skilled trainers in their own right, with loyal Pokémon willing to execute even their most evil orders. Some of the greatest villains are actually Pokémon themselves, angry at the world for a variety of reasons. Whatever the case may be, the strongest villains force Ash to rely on allies and the bonds he has with his Pokémon if he's to have any hope of succeeding. With that said, here are 10 of the toughest villains who were a real threat to Ash.

10 Malamar Almost Conquered the World

First Appearance: Pokémon XY, "A Conspiracy to Conquer!"

Malamar is a Pokémon who sought to conquer the world, intending to use a special machine to broadcast its psychic powers and take control of the world's Pokémon to act as its own personal army. Malamar's hypnosis was exceptionally strong, able to even control Pikachu and make him turn against Ash. It's not clear what drives Malamar to such evil ends, and it's quite rare to see a Pokémon behaving in an evil manner of its own accord.

It's not clear what drives Malamar to such evil ends, and it's quite rare to see a Pokémon behaving in an evil manner of its own accord.

Malamar appeared in two episodes, and was ed in the second by two other Malamar who had a similar dream of reshaping the world. Disturbingly enough, while Ash and friends were able to stop Malamar's evil plan, the trio of evil Malamar was able to escape, and are presumably still out there plotting domination.

9 Guzma Was Stronger Than He Thought

First Appearance: Pokémon Sun & Moon, "The Dealer of Destruction!"

Guzma is the leader of Team Skull in the Alola region, and has a long and complicated past with Professor Kukui. When Kukui announced the formation of the Alola Pokémon League, Guzma swore to destroy it. Guzma actually forfeited his first battle with Ash, as his Pokémon Golisopod retreated into its Poké Ball and refused to fight Pikachu. Rather than destroy the competition, Guzma ended up entering it, and made it all the way to the semifinals, where he found himself up against Ash again.

Unlike most villains, Guzma had something of an epiphany while battling Ash, realizing that his tendency to walk away from strong opponents really was due to an inner fear of losing. He and Golisopod went at Ash with everything they had after that, but it still wasn't enough. Guzma was angered, but faced his loss with surprising honor, allowing the competition to continue without disruption by Team Skull.

8 Lusamine Became a Monster Thanks to Nihilego

First Appearance: Pokémon Sun & Moon, "A Dream Encounter!"

While Lusamine herself is not a villain in the anime the way she is in the games, at one point she becomes possessed by the Ultra Beast, Nihilego, turning into a monstrous human-Pokémon hybrid referred to by fans as the "Mother Beast." In this form, she battled against Ash and his comrades, sending out her own Pokémon to slow them down and force the group to splinter off, until only Ash remained. Ash and Pikachu fought bravely to rescue Lusamine from the Ultra Beast, whose poisons were clouding her mind.

The powerful attack was able to shock Nihilego into releasing Lusamine, making it possible for Lillie and Gladion to rescue their mother at last.

Ash's Electrium Z crystal transformed due to being in Ultra Space, becoming a Pikashunium Z, allowing Ash and Pikachu to perform the 10,000,000 Volt Thunderbolt. The powerful attack was able to shock Nihilego into releasing Lusamine, making it possible for Lillie and Gladion to rescue their mother at last.

7 Mewtwo Could've Destroyed the World

First Appearance: Pokémon the Movie: Mewtwo Strikes Back

Mewtwo is an incredibly powerful Pokémon who was created by Team Rocket scientists set on making the world's strongest Pokémon. It possessed amazingly strong psychic powers, able to stop attacks in their tracks, and had created an elaborate cloning machine with which it intended to create a new world, inhabited only by clones.

Mewtwo was also responsible for creating the massive storm centered on its island, which was constantly growing in size and would ultimately have been a threat to the Kanto region, if not the entire world. It even battled the Mythical Pokémon Mew to a standstill, as the two were virtually tied in strength. Mewtwo and Mew's clash accidentally struck Ash as he attempted to interfering, turning him to stone instantly. The fighting ground to a halt, and the Pokémon's tears came together to revive Ash in a miracle. Mewtwo was moved, realizing the value of life, and put an end to its plans of destruction for good.

6 Cyrus Controlled Several Legendary Pokémon

First Appearance: Pokémon Diamond and Pearl, "Losing Its Lustrous!"

Cyrus is the leader of Team Galactic, whose evil plan was complex and involved multiple Legendary Pokémon. Cyrus had many loyal henchmen who could execute tasks for him in secret to avoid ruining his reputation as a businessman. He hired a Pokémon Hunter to capture the Legendary Pokémon Azelf, Mesprit, and Uxie, then used them to help control the even more powerful Dialga and Palkia, masters of time and space, respectively, with the Red Chain.

He hired a Pokémon Hunter to capture the Legendary Pokémon Azelf, Mesprit, and Uxie, then used them to help control the even more powerful Dialga and Palkia.

Cyrus dreamed of creating a utopian world, and used their powers to open a portal to another dimension, which he actually managed to escape through. However, Ash and friends, with the aid of Azelf, Uxie, Mesprit, and the champion Cynthia, were able to defeat the remnants of Team Galactic and free Dialga and Palkia, leaving Cyrus alone in his other world.

5 Pokémon Hunter J Could Turn Anything to Stone

First Appearance: Pokémon Diamond and Pearl, "Mutiny in the Bounty!"

Pokémon Hunter J was a poacher and thief who would capture any Pokémon on behalf of her black market clients, up to and including Legendary Pokémon like Azelf. Hunter J was in possession of incredible technology, including an airship with lasers and a cloaking device, and a cannon mounted on her arm which could turn anything hit by it to stone (or back). This made it exceptionally easy to capture targets, as they were rendered helpless.

Ash and friends clashed with Hunter J multiple times, each time emerging victorious by the slimmest of margins. After she succeeded in capturing Uxie and Mesprit, her airship was struck by Future Sight attacks which they had predicted, knocking it out of the sky and sending Hunter J to the bottom of the ocean, and her presumed death.

4 Ghetsis Could Mind Control Pokémon

First Appearance: Pokémon Black and White, "Team Plasma's Pokémon Power Plot!"

Ghetsis is the leader of Team Plasma. He "adopted" N and raised him in isolation, only allowing him with Pokémon that had been abused by humans in order to give N a warped view of the world and use him as a tool. He hungered for control over the world, and would stop at nothing to achieve his goals. He ordered Colress to develop a machine that would allow him to mind control Pokémon, which they ended up testing on Ash's Pikachu, although the power of their bond was eventually enough to overwhelm the device's control.

Ghetsis used the machine to take control of the Legendary Pokémon Reshiram, but Pikachu broke the control with a shock, freeing Reshiram and allowing it to take vengeance upon Ghetsis. After his defeat at Ash and Pikachu's hands, Ghetsis and Team Plasma's leadership were all arrested by Looker, an international police detective who had worked with Ash before.

3 Archie Held the Power of the Red Orb

First Appearance: Pokémon Ruby and Sapphire, "Gaining Groudon"

Archie is the leader of Team Aqua, set on increasing the size of the seas by using Kyogre's power. He managed to capture Groudon, an impressive feat on its own, while Team Magma took possession of Kyogre, forcing the opposing teams to deal with one another. Archie became possessed by an object associated with Kyogre known as the Red Orb, which drove him mad and encouraged him to have Kyogre destroy, even if it meant his own subordinates perished in the process.

Ash and friends, along with champion Lance, got caught up in the middle of this, and Pikachu wound up absorbing the Blue Orb, causing his power to overflow. Pikachu worked with Groudon to defeat Kyogre, causing the Red Orb to separate from Archie and freeing Kyogre from his control. Pikachu was subsequently freed from the Blue Orb as well, and the two Legendary Pokémon returned to their hidden homes.

2 Giovanni Was a Thorn in Ash's Side for Ages

First Appearance: Pokémon Indigo League, "Battle Aboard the St. Anne"

Giovanni is the leader of Team Rocket, and as such is Jessie and James' superior. Everything that the trio did was to please the Boss, so he'd been a problem for Ash for a long time before they actually met. The two only encountered one another once, during Pokémon Black and White, when Giovanni hatched a plan to use Meloetta to obtain the Reveal Glass, an object with which he could control Thundurus, Tornadus, and Landorus. However, when they lost control of Meloetta, the Reveal Glass's power took possession of him, encouraging Giovanni to destroy Unova rather than take it over.

Ash and Pikachu were responsible for freeing Meloetta, and once Giovanni retreated, were responsible for battling against the trio of Legendary Pokémon until Meloetta could calm them down. While Giovanni escaped, this was easily his greatest failure, and it was all due to Ash and his friends' interference.

1 Lysandre Unleashed a Deadly Threat

First Appearance: Pokémon Mega Evolution Special I

Lysandre was secretly the leader of Team Flare, and wanted to destroy the world so that he could rebuild it in his own way--without humanity. He sought to control Zygarde, a Legendary Pokémon responsible for protecting ecosystems, and eventually succeeded in this goal with Z2, turning Zygarde into a rampaging monster. While Zygarde was eventually freed, this was barely a setback. Lysandre also had control over a powerful object known as the Giant Rock, which radiated with Mega Energy, took a form akin to Zygarde's, and caused plant life to grow out of control and become dangerous.

Ash worked together with his friends, Alain, champion Diantha, and all of Kalos' Gym Leaders to stop the Giant Rock's march of destruction. Z2 and another Zygarde core, known as Squishy, combined to create Zygarde's Complete form, which finally possessed enough power to stop the Giant Rock before it was too late. However, even to this day, dangerous giant roots, caused by the Giant Rock, still appear and wreak havoc across Kalos, making Lysandre without a doubt the most dangerous Pokémon foe Ash has ever faced.