They aren't the most difficult battles that one encounters in a Pokémon game, but they are a test of strength to see if you're ready to progress. After beating the gym leader at a gym, trainers receive a badge to mark their completion. By collecting all badges in a region, one can move on and face the Elite Four.
Gym leaders are masters of their class of Pokémon and are meant to be taken seriously. We've seen various gym leaders over the years, and now, it is time to rank the most difficult. This is ranking the 10 hardest Pokémon gym leaders. Enjoy!
10 Valerie (Generation VI)
Without a doubt, Valerie is a tough gym to conquer if you weren't already familiar with the Fairy-type. Even to this day, a large population of Pokémon fans cannot name the weaknesses of Fairy-type Pokémon.
Poison and Steel are the only two elements that are super effective against Fairy, and they are relatively uncommon in the world of Pokémon. In generation six, it was overwhelming to include a Fairy gym leader when Fairy was introduced in the same generation. For these reasons, Valerie is one of the hardest gym leaders.
9 Koga (Generation I)
Because of his lineup of Poison-type Pokémon, Koga is recognized as one of the most challenging gym leaders. Getting past his amorphous sludge Pokémon, Muk, proves to be exceedingly tricky since it has high HP and uses the technique "Minimize" over and over while poisoning each of its opponents.
Koga is such a headache. It's no wonder why Koga was made a member of the Elite Four in generation two. His mastery of Poison-type Pokémon is incomparable.
8 Misty (Generation I)
After exiting Mt. Moon, you'll find yourself next to Cerulean City. The gym that occupies the city is empty until you find the gym leader elsewhere. These steps, along with her tough Pokémon, are why Misty is one of the tougher gym leaders.
At this point in the game, players most likely don't have an Electric-type Pokémon unless they own Pokémon Yellow. Also, since Bulbasaur is the least common starter choice, you probably don't have Grass Pokémon either. Her Starmie is a high level, and her techniques, which can be Scald or Bubblebeam (depending on the version), are devastating.
7 Fantina (Generation IV)
Hearthhome Gym is run by Fantina, a gym leader who specializes in Ghost-type Pokémon. Many people consider Fantina to be the hardest gym leader in Pokémon Platinum, Diamond, and Pearl. Not many people have Pokémon to combat the Ghost-type at this point in the game, so the match comes as a surprise.
Especially in Pokémon Platinum, it can be challenging to beat Fantina. She is the fifth gym leader in Pokémon Diamond and Pearl, and the third in Pokémon Platinum. Avoid immune Normal-type and Fighting-type moves to better your chances of beating Fantina.
6 Tate & Liza (Generation III)
The third generation of Pokémon games is considered to be the best generation by a significant number of people in part due to its leap in gameplay and amount of content. The introduction of tag-team battles was a major feat of the game.
Possibly the most challenging gym that you'll face in Pokémon Ruby, Silver, and Emerald, is run by two gym leaders named Tate & Liza. Since you're facing two trainers, you'll need a robust lineup, unlike previous gym leaders when having one strong Pokémon was sufficient. A sizeable lineup containing Pokémon like Xatu and Lunatone is why Tate & Liza cause problems for trainers.
5 Whitney (Generation II)
She's another tough early trainer to beat; Whitney is the third gym leader you'll face in Pokémon Gold, Silver, Crystal, HeartGold, and SoulSilver. She's frustrating to beat mostly because of the Milk Drink technique that Miltank uses.
Many trainers will be a lower level than Whitney's Miltank and not have Fighting-type Pokémon, which creates an agonizing situation where players run out of PP and white out. This is one gym battle people are relieved to beat finally.
4 Lenora (Generation V)
There are only a few Normal-type gym leaders in Pokémon. Lenora is a gym leader you'll face in generation five of the Pokémon games. Because Normal-type Pokémon have so few weaknesses, tied with Electric-type for the least, conquering Normal-type gym leaders is not easy.
Especially when you factor in the potions that gym leaders use, Normal-type is challenging to overcome. Lenora has two Pokémon, Herdier and Watchdog, but is exceptionally frustrating early on in the game for trainers who probably don't have Fighting-type Pokémon.
3 Giovanni (Generation I)
As the final gym leader in the first generation of Pokémon games, Giovanni proves to be a tough challenge for most trainers. His high-level Pokémon are significantly higher than what people are prepared for during that part of the game.
Evolved Pokémon like Nidoking, Nidoqueen, and Rhydon make beating Giovanni a grueling task. He is the leader and most powerful trainer in Team Rocket. For the aforementioned reasons, Giovanni is considered to be one of Pokémon's toughest gym leaders.
2 Clair (Generation II)
As the Dragon-type gym leader of Blackthorn City, Claire is the second-most difficult gym leader to face. Her tough to beat Pokémon include three Dragonair and a Kingdra. In the revamped versions of Pokémon Gold and Silver, HeartGold and SoulSilver, one of her Dragonairs is replaced with a Gyarados.
It's worth noting that Clair is the cousin of Lance, a member of the Elite Four and someone you'll encounter near Blackthorn City. She is the final Gym leader and because the Dragon-type has so few weaknesses, battling her necessitates steadfast training.
1 Blue (Generation VII)
His Pokémon are stronger than the Elite Four, which is why Blue (who is obviously based on Gary from the anime) is considered the most challenging Gym leader. Blue was a gym leader in the second generation of Pokémon games as well as in HeartGold and SoulSilver. He takes the place of Giovanni who has mysteriously vanished from the gym after disbanding Team Rocket.
In Pokémon: Let's Go, Pikachu! and Let's Go, Eevee! Blue appears as the Viridian City gym leader after you beat the Elite Four. His Pokémon lineup exceeds level 65 and contains mighty Pokémon like Mega Charizard, Gyarados, and Alakazam.