Hard fights in GD:
- Anasteria (max nemesis level)
- Fabius (extremely cheap)
- Loxmere (retarded)
- Alkamos (not really for a good endgame build)
- Those 3 guys at the end of Valbury (not extremely hard, rather a bit tricky)
- Moosilauke without Hoarfrost potion
- toxic/aether floors (more dangerous than everything above combined)
Impossible fight:
Ult Mogdrogen - I don’t know why this is even in the game. Yes I know he has been killed and even I managed to kill him with my first char on Elite, but this really shouldn’t be attempted on Hardcore above perhaps Veteran difficulty AFTER you’ve cleared absolutely everything else in the game.
This is a good guide an I agree with mostly everything, but I find it a bit over-detailed. If you manage to make a good build and are a fairly experienced player you’ll already know what to do, just use common sense. Hardcore isn’t for begginers anyway, I’d advise finalizing at least 2 non HC characters before attempting HC.
I’ve managed to survive ult with my supossedly glass cannon Warlock with only 4 deaths (3 from stupidly trying to take on Mogdrogen alone and 1 from some crucible co-op lag bs). You just have to be cautious, know the maps really well, have (over)capped resists and a good build and also learn to kite well when needed (not really hard to learn).
But at the end of the day HC is also played for the thrill of it and not like putting paper towels under your brand new sneakers not to get dirty. At least that’s my opinion, I just love the gamble and I couldn’t play the game in the “safest possible way” anyway. With my HC warder I jumped right into Depraved Sanctuary as soon as I got the key, popped the portal and went into the fight with at least 5 levels higher Salazar. I’m also planning to go into SoT around lvl 20, which is usually not advised exactly.
But to be completely honest I’ve already gotten a bit bored with replaying the same content over and over again and HC thrills like that are the only thing that still keeps me interested 
