>>55185988>HardestIf you factor in post-battle facilities, then the sheer RNG and time of Emerald's Battle Frontier makes it the hardest game. If not, then probably any of SM/USUM and BDSP since in-game boss characters actually have EV-trained Pokemon. I'd even throw some battles from Yellow and Platinum in there, but they're not even close.
>EasiestSword & Shield, without a doubt, though it was remedied by certain dynamax bosses like Mewtwo and Zeraora that required legitimate strategy. XY has some spikes but becomes a steamroll after Korrina. Original DP is trivial if you have a Bronzong on your team.