While playing through BW2, I noticed that I had a lot more trouble on the gym leaders than in past games. I like that they bumped up the difficulty level, but I didn't expect to struggle this much on the gym leaders...

Here are some leaders that I had trouble with:

1) Cheren- He kicked my butt with his Lillipup after using Work Up twice. I even recorded my failure in that battle.

The only tough one was the one in Castelia. No fire types was "nice."

Skyla...


and...


her...


freaking...


...


SWANNA!

I swear that this thing nearly made me go insane. Not having an electric type, or even a pokemon that new an electric move, made this battle a living nightmare.

A tough choice between these 2 demons.

1- Cheren. Work Up screwed me over TWICE. I had to sit and think of a way to beat him as I grinded for Force Palm (Which I never got)

2- Clay. Excadrill is like a living nightmare. It's fast and tears through almost ALL of my team easily. Crobat was the only thing not weak to it, and amazingly it ALSO had to be the only thing that couldn't damage it. Well, there was also Servine, who won the battle for me, but that was tough.

See, you guys are making me chuckle with your Cheeeeren, and your Buuuurgh, and oh, wow, that Swaaaaaaaaana that everyone seemed to hate so much (kicked to the curb by my Ampharos ), and then Claaaaa-- AALY CREAP DIS GUYS A JURK!!!

Seriously, Clay was the one that got to me. I had a Water type with Razor Shell, and that Krookodile still managed to down my whole team the first time with its...pure evil tactics...*shudders*

Drayden. Having no Pokemon that can use Ice or Dragon moves makes fighting dragons a right pain.

Elesa's probably second with her Volt Switch spam.

Cheren... I started off REALLY bad.

Burgh takes second because I didn't have any pokemon that gave me the advantage.

I didn't have anybody who particularly made me frustrated, though Volt Switch with Elesa was a PAIN, and it got old really quickly. Considering I'm only about to battle Skyla now though, I can't say much about the last few gyms. I do have an Ampharos and an Arcanine with electric moves, so she should be simple... Clay's gym has been the easiest. None of my Pokemon even fainted. You guys are so cute with your, "Uuuuuuuugh gyyyyyym leadeeeeeeers."
EDIT: Defeated Skyla. One-hit all of her Pokémon except Skarmory which had Sturdy. Gym leaders are eeeeeasy.

I would probably say Drayden and his dragons.

Burgh, I hadn't caught any Pokemon since my starter against him, so I resorted to catching a Scraggy which still failed badly.

Drayden is second, I did really quite badly without any ice/dragon moves.

Everyone else was easy(ish), save Elesa and Roxie, who were slightly difficult.

Really though, Clay was one hit kills for everyone for me. No one fainted, my Scraggy and Servine wiped his entire team out in a flash. Ad Cheren wasn't a problem, even with just Snivy.

Now that I've beaten all the leaders I can say it was the ones before, and in addition there's Drayden and his gym. His gym was extremely tough, especially since I'm one of those "Battle every trainer" type people, so I had to leave and heal often. Or waste a lot of my ~150 Fresh Waters every few minutes. He himself was not as hard as his gym, but he was sure a threat.

Really, guys, my team was just STACKED. I found no trouble with any Gym leaders... except Cheren.

Really, I had caught a riolu, and I was set to spam Counter. I didn't exactly expect him to use work up ALL 6 TIMES!

Took out all my pokemon in 3 hits.

The rest were sort of easy, though. My final team was:
Samurott (covered the ground gym)
Lucario (should have covered the normal gym, but instead ended up covering the dragon gym... Ice Punch ftw?)
Ampharos (covered the flying and water gyms)
Arcanine (covered the bug gym)
sandslash (covered electric gym)
Flygon (helped cover the dragon gym)

The only thing I didn't had anything to cover at the time was Roxie's gym. However, I still sweeped her pretty easily. Guess I got lucky? xD

Drayden.

Every. Single. Pokemon.

I raged so hard the first three times I battled him, but, luckily, I won in the end.

I SHALL NEVER DO THAT EVER AGAIN

Elesa was a pain for me in both BW and BW2. I never seem to have a Pokemon that resists her Emolga's Volt Switches. I struggled a lot just trying to have one of my Pokemon stay in long enough to deal enough damage to knock them out.

Easily the last one for me. I forget his name. Speedo guy.

His stupid Jellicent was the perfect match against my Emboar. I had to go and grind for several hours to level up my Virizion. SO annoying.

I don't know why, but none of the Gym Leaders were that bad. In fact, they seemed waaaay easier in Black/White II compared to their prequels. Do you think it was because I had a Genesect? (<3???)

I can say Drayden was the biggest annoyance for me, though.

Let's see...
Clay, Excadrill killed my Lucario and my Emboar each in one hit, took around five times, maybe, to beat him.
Drayden, my only Ice or Dragon attack was my Vaporeon's Aurora Beam. But then again, I had my Genesect!

Hardest were:

1. Cheren- I hate Work Up with a passion but none other than Riolu being the total beast he is, managed to win the fight with like 2HP.
2. Clay- Excadrill, Nuff said.

If you get, like, a Krookodile, you can KILL Clay. I keep my Pokemon 5 levels from disobeying, so I only have to level up 10x per beat. However, Elesa... AARGH. She wouldn't stop spamming volt switch!
Elesa was the only one I lost to. I didn't need a Magnemite for Roxie either. She wasn't too hard. What should I catch after Skyla hits the floor? (My new Joltik needs leveling.)

If this post was stupid, I blame my parents.

The only one I really had trouble with was Elesa, for an obvious reason- Volt Switch.
I didn't lose to her, but I sure was close. >.>

Cheren. I had Riolu, but no Force Palm. FAIL RIOLU! Or I fail for not training it... No, def Riolu's fault.

Drayden. Just eff him

Well, I'm only up to battling clay, So Cheren would've been the hardest for me. (I only had a Snivy and Mareep) Followed by Elesa, I had no good pokemon to battle her with so I had to use my Mandibuzz >:0 (I was lucky, she only used volt switch a couple times)

Going on my experience playing mono-Grass runs...

Cheren: Not too hard, but not a cakewalk either. Train right and he's easy-peasy.
Roxie: A little more challenging, but not tricky either. Dat Venoshock tho
Burgh: Also not that particularly difficult, despite the type disadvantage. But Bug-types are generally not hard to work around.
Elesa: Not too tough, Volt Switch strategy is a little annoying though...
Clay: Easiest Gym Leader for me.
Skyla: For me, it's only natural that Skyla would be hard. For others, since it's placed right in front of a cave with ELECTRIC-TYPES, she's probably pretty easy for others.
Drayden: Haxorus + Dragon Dance = Death.
Marlon: For me - easiest Gym Leader by far. For others, probably somewhat more tricky, but still he doesn't seem very difficult.