The Elite Four, aside from the Champion, is the best of the best when it comes to Pokemon trainers.
The majority of regions have an Elite Four. Trainers defeat the Gym Leaders in order to be able to take on the Pokemon League. That is where the Elite Four waits as the pathway to battling the Champion.
There are truly some Elite Four members who can be classified as a cake walk. They aren't difficult at all. Some of the other Elite Four members, however, are nearly impossible to defeat. The Elite Four trainer and their Pokemon are as strong as it gets.
Top 5 strongest Elite Four members in Pokemon
#5 - Agatha
In the Generation I games of Kanto, Agatha is an incredible threat to go up against. Many trainers won't have much experience with the Pokemon she uses in battle. While she is hyped up to be a Ghost-type user, all of her Pokemon have a Poison-typing. She also has two Gengar.
#4 - Karen
Karen is the first Dark-type member of the Elite Four, appearing in the Generation II games and its remakes. With tanky Pokemon like Umbreon, Vileplume, and Gengar, Karen can be serious trouble for trainers. While Dark-types are weak against Fighting moves, Karen has a Murkrow on her team to counter that. Truly, she has thought of many ways to deal with those trainers who make it to her stage.
#3 - Caitlin
Caitlin's Psychic-type team is incredibly powerful. As the last member of the Unova League Elite Four, she deserves her spot. The team has a well-balanced mix of supporting Pokemon, Special Attackers, and Physical Attackers. Going against her a second time is where her true power shines. She adds a Metagross and Bronzong to the team, making her that much more challenging.
#2 - Lance
Lance is the first Dragon-type user players encounter in an Elite Four scenario. In Kanto, Lance is the most difficult challenge that trainers will face. He may even be more difficult than the Pokemon League Champion. His team consists of Gyarados, two Dragonairs, Aerodactyl, and Dragonite. The first four Pokemon will have no problem chipping away at any team, leaving Dragonite to clean up.
#1 - Drake
Drake is another Dragon-type Elite Four member, representing the Hoenn region. His team is incredible. Any trainer would be lucky enough to have just one of the Pokemon he uses. Salamence is his ace-in-the-hole and in the remakes of Ruby and Sapphire, it can Mega Evolve. Some may believe he is a pushover in the remakes due to Fairy-types, but they are dead wrong. In the original or remakes, Drake is the most powerful Elite Four member.