Let's see, I started off with Torchic.
Roxanne, I hate your big NOSEPASS!
Brawly, I had a tough time with until I figured out Swellow's flying moves were super effective against his fighting Pokemon.
Wattson. I hated his Magnemites and Manectric. So hard to beat him.
Flannery, was pretty easy. Never had difficulty with her.
Norman, never knew what to use. (Didn't know fighting moves were super effective against normal types back then.) Slaking was annoying.
Winona, trouble for me as well. Especially Altaria.
Tate and Liza, had no idea what to beat them with. Hardest time with them.
Wallace, not that bad. I had a Raichu by then.
Tate and Liza were the most annoying IMO.