shinee hates me tbh :D. their common took me forever to finish. the rares weren´t that hard. I had no intention to complete them apart from getting minho´s rare, but I was VERY lucky that people around me got their rares and I got offered them.
otherwise, I think AB6IX was SO hard when it comes to waiting? no one else was collecting them at that time but I had to do a reroll after a reroll to finally get the last card. I also felt like they were stuck in there :D.
iKON, but I think it was more my impatience than anything. I wanted to finish that set super quick for some reason and I was always so moody when I couldn´t trade for a card, that is probably why I remember the set being hard to finish while in reality it probably wasn´t.
any other huge set is definitely a struggle if it is new because it is a lot of waiting.
OMG I KNOW WHICH ONE, ATEEZ COMMONS!!! still haven´t finished :D I only have the rare set and I´m done :D