My review on the gym leaders:
Falkner: His first Pidgey is puny, and easily one hit KO'd. However his Pidgeotto can be a pain, because it spams roost and its tackle does more damage than you would expect. This battle is tough if you have underleveled pokemon, otherwise it's just lowering the Pidgeotto's defense and then spamming your strongest attack.
Bugsy: Would you call him a Gym Leader, or just a trainer that has pokemon that are about 5 levels higher because the others are all way too weak? Yes, I am talking about harden. It really sucks. I don't see anyone not defeating his Metapod or Kakuna. But then you get scyther. It can be really annoying if it gets sent out early, because it will spam U-turn. Luckily, if you use any fire type he's easily swept.
Whitney: Unfair. She starts off by using her Clefairy, which can lower your HP by quite a bit. The real problem is the Miltank though. Milk drink, rollout and the potions make it deadly. If you didn't train seriously hard, this gym battle will be seriously hard.
Morty: Yes, an average gym leader, finally. After Falkner and Whitney you expect this to be worse. But it's not. He's easier than Whitney. The problem for him is, he uses only the evolution chain of Gastly, as there aren't many ghost types in Johto. Other than that, his Gengar is the only actually good pokemon that he has, making him even easier to deal with. But his Gengar's spamming might be something to worry about. Make sure you have an anti-spam pokemon with you, and you should be fine.
Chuck: He can be easy or hard, depending on how you fight. His Primeape shouldn't be so hard, as you can bring a psychic type and defeat it easily. Then, the overleveled Poliwrath who knows overpowered moves comes. If you have a pokemon with swift or even better aerial ace, this will be no challenge. However, if you don't, then :t300: . That's how weak your pokemon becomes, not the pokemon you should use. I swept him with my Typhlosion, but he was level 35 or so, while the others were 25 or so.
Jasmine: I swept her with my Typhlosion. If you picked Cyndaquil or Totidile, she is easily swept. The problem comes with a Meganium. Also, if you started with a Meganium, it would be a good idea to get a Growlithe for this gym, as it will stand a way higher chance of winning. Not much else to say here, except when she uses hyper potions, she can be annoying.
Pryce: Swept with my Typhlosion. Typhlosion is really handy through this part if the game. If you use it, you will easily win. If you use an Arcenine, you will also be likely to win. His seel is a bit annoying, it's not weak to any starter. Same with his Dewgong, except it knows better moves and stuff. The Piloswine is easy to deal with. It is not water, so fire can knock it out pretty easily. Back to Dewgong: A big problem is that it has sleep talk, so sleep doesn't affect it much. Your pokemon will probably be underleveled due the wild pokemon lacking strength. Dewgong can be dealt with more easily by lowering its special defense and spamming special attacks.
Claire: Overpowered. This is a really unfair battle. To start, wild pokemon aren't even level 25 in ice cave. Then you battle a bunch of overpowered trainers that spam. Problem is the Kingdra mostly. Its Dragon pulse can easily deal a lot of damage, but hydro pump is just unfair. Claire has had too much training, and I don't like that. Additionally, it is really hard to get something that's strong against dragon types at this point. Her Dragonairs's shed skin abilities are annoying, since status effects won't have much effect. Why is she even more overpowered? Because of healing. A really unfair leader.
Claire is the hardest leader in my opinion.
