I like my headcanon where Raihan just doesn't know how to build a competent singles team, much like how most singles-focused players have no idea how to build a competent doubles team.
pssh, i mean, you still use stealth rock, right???
right????
Maybe she's not the hardest but Candice in Platinum has a Froslass, which only had Snow Cloak back then, with Double Team.
Y'know in my Infernape run (s/o to sinnoh for having all hitters in the starter department btw!) i assumed this was going to be annoying - my team was Infernape/Roserade/Mamoswine/Magnezone/Vaporeon/Yanmega and i had just rid the world of her first 3 ice types, unsurprisingly - with my boy Infernape. Then her Froslass comes in with an evasion strategy so dastardly most hardcore Smogon-goers would bust a vein just lookin at the move set. i wasn't too thrilled about fighting this thing and risking a Psychic KO, so i switch to Magnezone. With the Double teams, Blizzards and hail chip piling on, my Magnezone would no doubt be overwhelmed....
until i remembered i still had Lock-On as a move. So rather than an infuriating evasion hax game, i ended the match in roughly 2 turns with the Flash Cannon TM i nabbed from Byron (three guesses as to how i dealt with him). I would then go on to use this strategy in my Platinum Steel Locke as well, but with Probopass since that thing's got a mammoth SpDef stat.
But anywho. That's enough from you fellas. Let's hear on an NPC i think is pretty damn difficult.
Platinum. Lucian.
Obviously, the Final Elite Four member of Sinnoh is gonna be a toughie, but more often than not, this dude is consistently an ass-kicker if you're not prepared. Let's start with his team.
It ain't just the old standbys of "the Bronzong with one weakness, and you better hope you don't take an earthquake" and "Alakazam's Focus Blast missing? What's that?" now you have to fend off an effectively upgraded Medicham. Say hello to Gallade, who's likely gonna be guarded with some screens when he comes in, as if that nuclear coverage isn't enough of an annoyance. If you think that your good old Weavile is comin in and takin names, you better be ready to play with some fire, and you just faced Flint a while ago! Of course, his Espeon isn't as nearly as annoying, but Signal Beam can still screw you over if you're not prepared, so i still take it as an upgrade to the Girafarig.
Sheesh. If that's what you gotta take down before the infamous Cynthia, I got your work cut out for me.