ny specific examples through your gameplay?
The entirety of Blighttown. You have to pass narrow walkways with mobs blowing toxic darts at you. The hell hounds show up in two or three numbers jumping you along with another asshole that tries to grab and bite you. Near Queelags entrance you have three or four stonethrowing fat boys making your life a living hell as you trying to get in to her (or out). Not to mention these irritating flies that show up in infinite numbers if you are not careful. Top that off with a poisonous swamp. Not too mention Lautrec who ruins the day when you finally get up from that godforsaken place.
Other parts of unfair moments is the entrance to Capra Demon where you have a split second to realize that you are gonna get gangraped by a huge goat demon and his two mutts. Also, the arena is so small that you can barely dodge at all.
The gauntlet in the Parish with a huge pig bum rushing you when several dregs attack you with bow and arrows. The are also multiple dregs that rush you in a narrow corridor on the way to the Gargoyles. They also have a channeler that shoots soul arrows at you and boosts the dregs.
There are multiple enemies in the lower burg ganking up on you with dogs and ninjas swinging all over the place.
Anor Londo is ripe with silver knights shooting arrows at you. The ceiling with the painting guardians is also bullshit.
Bonewheels in Catacombs. The Tomb of Giants is just one big pile of unfair middle fingers thrown at you in rapid succession.
And the bosses in Dark Souls 1 have a few lackluster bosses too. Taurus Demon, Ceaseless Discharge, Pinwheel, Bed of Chaos. Centipede Demon. And if you want to talk reskins the Asylum Demon came in three different versions in the same game. And two the most famous gank bosses in the series can be found in part one. Just saying.
You mention optional areas in Dark Souls 1 and how you can avoid most of Blighttown, but the Doors of Pharros is optional too, and you don´t have to engage the rat. Magus and Covetous are just minibosses on the road to the Duke and Mytha. I agree that they are shitty bosses but these types of bosses have been in all three games, but you are acting like this is exclusive to Dark Souls 2.
The point is that all of the four Souls-games have these types of encounters, they have similar areas and similar sort of design, some less and some more. Poisonous areas is a staple in the series since Demon´s Souls, like Death Mountain in Zelda or the fog in Silent Hill. But everywhere on the Internet people are acting like Dark Souls 2 was the only one to have this kind of design, this "hard for the sake of being hard" when the other games present similar challenges too.