>>26966599HGSS is pretty hard, due to the difficulty of replacing people, but that might just be more tedious. The Elite 4 is surprisingly difficult as well.
Vanilla gen 3 is pretty hard, because most Hoenmons are utter shit until gen 4 saved them from the dumpster. You know things are bad when a Zubat is one of the better catches.
X and Y is the easiest, even assuming no EXP share, boxed starters, Lucario, and Legends, and no megas.
ORAS is weird. It can be quite difficult, or a complete cakewalk depending on what your team ends up being. The varying amounts of buffs pokemon have received over the years really shows. Dexnav also might make the "First Pokemon in an area" less restrictive than usual, you may need to self-rule your way through those.
