"Most Hellish Area: DA:I Base Game"
This is difficult for me because the game was so trivially easy and breakable. I have soft platinumed this game (base, not DLC), and the nightmare run I did past the halfway mark was a breeze.
I would say the most annoying areas are the Hissing Wastes (long areas of nothing, ridiculously stretched puzzle pieces, infuriating to first-time-find High Dragon), and the Exalted Plains/Dalish Area (psuedo-same spacial problem, double war-table extraneous missions for areas that should have been reachable without using power, boring overall feel with infi-enemy spawning and stupid evasive Horrors).
As far as worst area in the game, believe it or not the Ferelden Frostback approach in the Hinterlands after the camp. The absolute balls the developers had to put an arbitrary cap on health potions and then create an area in which you are assaulted by scaling enemies with more-than-normal health while having damage hurled at you via fireballs astounds me. Granted, this is circumvented by a mad dash to the enterance of the lair, but regardless it infuriates me that the fight was so dismally simple that they had to add a tax to it in order to try to make it difficult.
Other than that, after the half-way point due to armor and weapon crafting, potion upgrades, and ability knowledge (ie. I have played an RPG before and understand what is a skill tree) I never had a character aside from Bull (Looking at you, AOE soaker) ever get close to death, and even if they DID, I just had the invicible Viviene put a buble around herself as a Knight Enchanter, revive said character, and immediately boost-barrier them while they chugged a potion.
Of course, there were a few other places such as certain fade rifts where they would spawn multiple Dodging Despair Demons, or the Exalted Plains/Dalish Area dungeon in which Dodging Teleporting Arcane Horrors would keep spawning, sometimes in the multiple.
/wrists