i think whitney's milktank is the hardest pokemon and clair's kingdra or dragonair

Mostly because it took me months and I mean months to defeat her Miltank and attract combo especially without Ice Punch which I had in Crystal,Regular Gold and Silver..the TMs in the department store were so different and I didn't have my Ice Punch which lead me to lose so much to her in Soul Silver.bah.

Her rollout attack was frustrating

i didn't have any problems with Whitney, but i did with Claire. you cannot believe how many times I've reset my nintendo DsiXL. i only won against her because i kept commanding Nidoking to use thunder, other than that i would have miserably lost.but when i battled Whitney, it was easy cause a few of my pokemons had fighting type moves.

Jasmine is by far the easiest.

Ughh I remember trying for hours to defeat her Miltank since it kept using attract it didn't help that my team was all boys..

They were both tough to battle, but it took me months to beat Clair. I barely won with Dewgong, and it was a good thing her final Pokemon was Rhydon. My Dewgong barely had any HP, and I had a 1 hit K.O. with surf. It took me a couple of hours to beat Whitney's Miltank.

She was so hard to beat!