>>45570126>Monkey TroubleReasonably dangerous, both Pokémon buff themselves and their ace is strong against your starter. Lillipup can flinch with Bite and steal your berries with Pickup, Pansear can destroy berries with Incinerate. You shouldn't lose with your own monkey (or any full team) and your free Fresh Water, but you can't let them set up.
>CherenLike the last gym but with less counterplay. You could hunt down a 5% encounter Riolu and grind it to 15 and annihilate everything, but if you don't do that you'll be dealing with two pretty decent attackers who buff themselves and hit you with 50 power STAB Tackles. With a full team and free Fresh Water you'll probably be fine.
In Challenge Mode he also has a Pidove, but it doesn't have a Flying move and still gets destroyed by Riolu's Force Palm.
>ViolaHas a surprisingly tricky team that might pose a threat if you couldn't trade for or catch a Farfetch'd with Aerial Ace in the same town.
>IlimaThis dude has a fucking Smeargle
>MiloYou have an insane amount of options to deal with him and he only has two Pokémon, total pushover.
TL;DR
None of these are dangerous with game knowledge and any challenge is removed by overleveling. The game's only as hard as much as your options are limited; none of these teams are going to reasonably wipe your own team of six (maybe the Unova leaders since they can theoretically buff and sweep, but you'd have to be really unlucky, underleveled or stupid for it to get out of control like that). Roark's Onix debuffing you becomes a non-issue just by playing on Shift.
Limiting yourself, say only being guaranteed your starter and as many other non-selected Pokémon as the Gym Leader with no overleveling or healing, I would say the hardest is probably Cheren's fight since it's just a slugfest with no type advantages to exploit and he has access to buffs while you can only debuff.
