>>35450417gen V saw the rise of Eviolite rendering both Misdreavus and Dusclops as superior spinblockers, power creep negatively affecting its high defenses and just generally not standing up to UU and OU's strongest threats
gen VI means that everybody and their mother gets access to a 130 BP move that hits Dusknoir, already reliant on Lefties and other items for recovery, extremely hard despite 130/130 non-HP defenses. Fighting types, despite their massive nerf in the form of Fairies, are no longer useless against a bulky ghost like this bro. Kangaskhan has scrappy and power up punch and outspeeds, so can substitute against wisp and boost twice before mega evolving and also using Crunch twice in one turn, not to mention being immune against Dusknoir's only priority. Mega Lopunny later on wasn't much of a help either because Hi-Jump Kick WILL deal damage.
TL;DR, every single advantageous matchup Dusknoir had in Gen IV was either lessened or nullified. It competition also picked up some key merits that Dusknoir did not. Fuck GF they ruined one of my favorite cross-gen evos of all time.
