>>116620
Technically its one of the hardest, but also not really, its more like its just balanced poorly in its difficulty curve and the way things are handled.
Radiant Dawn is weird, and its also a sequel to the gamecube game, Path of Radiance, which was one of the easiest in the franchise.
FE5 might be considered the hardest, partially because its mechanics are autistic and tedious, and the maps are pretty much "anti-player".
FE12 (the Japan only DS game) on the hardest setting, FE14 Conquest Lunatic, FE5 (Thracia 776), FE6 Hard Mode, and Radiant Dawn are the hardest FE game modes generally speaking, if you don't go into too much specifics on the others and whatnot, but it gets more complicated the more you add into the mix