That One Boss.

[レイジングブラスト]

Even if I have an electric type on my team I'll always end up getting my ass handed to me by Wallace in Emerald. Maybe if the Hoenn electric types weren't so horrible I could beat him on the first try.

 

[solarowl]

Blue in HGSS. I hated his Arcanine.

 

[WildEagle]

Whitney, her Miltank's rollout never miss against me wtf -.-"
Elesa and countless spamming of Volt Switch and Double Team.

 

[jab2033]

A non-gym leader example: That Gyara and Raichu double battle on the fog route in DPPt.

That's the only non-gym/E4 battle who's managed my KO more than 1 of my pokemon. I beat them, but that Gyarados is a pain.

R/S Norman was very tough for me because of his Slaking.

Took me 3 times to beat Norman first time in Emerald. Yeah, even with a Blaziken. I was a little underleveled at the time, and I kept on burning Slaking, which would then Facade my Blaziken and the rest of my team.

I remember in GSC, Whitney always kicked my ass with her damn Miltank.

She's just as difficult in HGSS, too. At least the GSC Miltank didn't have Scrappy.

 

[インフェルノの津波]

Okay. I will admit it:

Cheren after the Main Storyline is freaking hard with his Haxorus. It's not as broken as Hydreigon, but it's Outrage makes me use Outrage.

 

[Tumalaz]

Whitney and Norman. Seriously.