10 Hop
Just like in every Pokemon game, you get a rival and in Sword and Shield, it's Hop. Unlike in other games, Hop always takes the pokemon that gives you the advantage when it comes to Type strengths and weaknesses. But you can't just rely on Type advantages against him, especially since he'll take any opportunity he can to hold a type advantage on you!
Some of Hop's strongest Pokemon are his Snorlax, Corviknight, and Trevenant, which he has when you run into him on the way back to Hammerlocke. He also acquires either Zamazenta or Zacian, depending on which version of the game you have, and will use it during his Champion Cup rematch against you.
9 Bede
Bede is another rival you encounter during your journey and though he's arrogant, he has the skills to back up that attitude. He starts off with a team full of Psychic Pokemon, which can be hard to beat if you hadn't had a chance to catch either a Bug, Ghost or Dark-type Pokemon.
His Pokemon know attacks like Confusion, Light Screen and Reflect that can make battling him tough if you aren't prepared to counter against these moves. After his defeat in Stow-on-Side, his team is made up of dual-type Fairy Pokemon which makes Dark-type moves a little less effective on his Pokemon.
8 Marnie
Marnie is another rival of yours that you'll encounter when you go to register in Motostoke. You won't have as many battle encounters with her as you will Hop and even Bede, but each battle will be a tough one. Nearly all of Marnie's Pokemon are dual-types, meaning you'll really have to choose carefully when it comes to picking which Pokemon you send out into battle.
Her Morpeko is as tough as it is cute, and she will use a potion to heal her Pokemon at least once during the battle. Several Pokemon on her team can also use the move "Torment", which keeps you from using the same move twice in a row.
7 Oleana
Throughout most of the game, Oleana appears to just be Chairman Rose's assistant that keeps him on task. While appearing cool and collected, when you face off against her at Rose Tower she loses her composure and shows she's a fierce battler as well.
Oleana's team is made up of a variety of different Pokemon types, all who have moves that can be used in a combo to deal a lot of damage. For example, her Froslass has both "Will-O-Wisp", which inflicts the Burn condition and "Hex", which deals double the damage to a target suffering from a status condition.
6 Sordward
After the main storyline, Sword and Shield both have a post-game storyline. When you and Hop place the Rusted Sword and Shield back onto the altar, two people with the craziest of hairstyles, arrive. They claim to be the descendants of the first kings of Galar and will take the Rusted Sword and Shield and challenge you to a battle.
If you have Pokemon Sword, then you'll face against Sordward who has a team of level 60 Pokemon who all know moves that deal a lot of damage, and moves that help buff their attacks. Most of Sordward's Pokemon are also dual types, making it a little difficult to choose which Pokemon you want to send out based on Type effectiveness.
5 Shielbert
Shieldbert is the brother you'll fight if you own Pokemon Shield and you'll face against him once in the Slumbering Weald while Hop faces Sordward, next in a multi-battle against him and his brother, and then finally at the Energy Plant. Shieldbert's Pokemon are also level 60 and above and have powerful moves at their disposal.
However, Shieldbert's Pokemon also know several moves that protect them from damage and reduce the damage they take, like "Protect" and "Light Screen". He has only one dual-type Pokemon, Bronzong, and his other pokemon are either Fighting types or Steel types.
4 Raihan
Not only does Raihan specialize in Dragon-type Pokemon, but he also specialized in moves that cause a sandstorm. At this point in the game, you've discovered that the changes in weather you encounter has a pretty big effect on your Pokemon.
Raihan's Pokemon can use moves that cause a Sandstorm which will not only damage any non-Ground, Steel or Rock-type Pokemon you have on the field, but it will also boost the special defense of his Gigalith. Raihan gets even more fierce in the finals of the Champion Cup, as his team is made up of Pokemon that all-cause weather effects.
3 Game Freak's Morimoto
While exploring the hotel in Circhester you might have come across a police officer named GAME FREAK's Morimoto, fans of games as far back as X & Y might know that Game Freak's Morimoto is a recurring NPC, based on game designer and programmer Shigeki Morimoto. Once you become champion you unlock the ability to battle him in a double battle.
All his pokemon are level 65 and have lots of health and moves that help protect them from your attacks and keep their health up. Game Freak Morimoto can also Dynamax his Snorlax, further making this battle one of the tougher ones, but it's worth the challenge as defeating wins you the Oval Charm, which boosts your chances of getting eggs from the Pokemon Nursery.
2 Leon
It probably isn't a surprise to see that Leon, the Galar Champion is on this list. He's who you've been training yourself and your Pokemon for and he shows you why he's the undefeated champ during the Champion Battle.
Where Hop took the starter that has a type disadvantage against yours, Leon takes the one that has an advantage over your starter pokemon. All of the Pokemon on his team are above level 60 and know some pretty powerful moves like "Outrage". He can also (and will) Gigantamax his Charizard.
1 You
That's right, you are the strongest Trainer in both Sword and Shield! Technically, at least. You start off in-game with no Pokemon at all until Leon gifts you a starter of your choice and in the end, it's you who finally defeats the "unbeatable" Champion and claim his title.
If that isn't enough to prove that you're the strongest trainer in both games, the fact that you're one of only two trainers to have a legendary pokemon, (Zacian or Zamazenta depending on which version you have), but you're also the only one to have the fearsome Eternatus on your team.