Now overall, no gym leaders on a Pokemon game are CRAZY hard, but the ones that sticks out as pathetically weak pushovers were...Well, this...And going in each regional order.
Kanto
Brock: Bulbasaur and Squirtle sh*ts on Geodude and Onix.
Lt. Surge: Tch. Diglett. And you didn't even halfta level it up.
Giovanni: Was pathetic. At this point you'll have all alotta powerful attacks at ur disposal. I mean, Ground Types? Pffft.
Johto
Jasmine: Was the only easiest Gym leader for me...Strange, I know...But Quilava and Fera can make easy work outta her Steelix and Magnemite aren't anything anyways.
Hoenn
Winona: Now most of all the Hoenn gym leaders were poweful, but Winona was a cakewalk compared to the rest. All her Pokemon were generally weak...and the quickest way to deal with her Altaria was getting Ice Beam from the Abandon Ship...
Sinnoh
Maylene: She's wasn't hard for me...PERIOD! Lucario went down rather easily. Having low defensive stats was downfall, yo.
Crasher Wake: Again, another gym leader relying on a Pokemon with low defensive stats. lol Floatzel was kinda hard tho...since it was fast, but I was able to one-shot it with a powerful enough Super Effective move.
Candice: Oh, mah god...Seriously? I honestly have no comment. She was the weakest outta all gym leaders.
Unova:
Now, almost every gym leader on B/W and B/W2 were just. *sighs* Well, with the exception of Lenora and surprisingly...Cheren. Let that Lillipup power itself up with Work Up if u want to...you'll be wipe out, before u can blink.
The Trio Brothers: All three were pathetically weak; Pansage, Panpour, and Pansear didn't really put up a fight. I destroyed them, before they could even begin to muster an attack.
Roxie: Nice gym, nice gym theme...but that's pretty much it. I whooped her ass and then sent her crying back to her daddy. *shakes head*
Burgh: Mm, he was actually harder on the original B/W; but that not saying that mean much. B/W2 was just a stepback for him. A Swadloon and a Leavanny? Dafaq?!! Really?!?!?!? And his challenge mode battle wasn't really...challenging.
Elesa: On both B/W and B/W2...the experience was still pretty much the same. Thrash her ass and went on mah way. It was like this for almost EVERY gym leader.
Clay: Clay was actually harder on B/W2...seriously...But then again...that's not really saying much. Da only Pokemon of his that puts up a fight is Excadrill...but itself is kinda fragile too.
Skyla:
Arguably, the weakest Gym leader on the game. Her Pokemon are so weak...Swanna as ur lead Pokemon is a no-no. But hey, I like her gym theme on B/W2.
Drayden/Iris: Were the hardest, easiest gym leaders. lol Only reason why I added him to this list, cuz none of his Dragons could do anything against mah Pokemon. For cryin' out loud on mah B/W2 run, I had knockout Drayden's Haxorus with a Leavanny. Attract and X-Scissor.
Marlon:
I like that they added new gym leaders to this game...and Marlon's pretty cool, but his Pokemon aren't. Pretty much owned him.