As a bonus, here were the most annoying cards to get, in my experience:
King Thordan - because even though you can solo it, each attempt still takes like 5 minutes because it's basically an autoscroller.
Archaeotania - drops only from Dream Triad Packs. Drove me absolutely insane, I honestly think I bought over 40 of them before I got it.
Frixio - drops from two NPCs, one of which is MARCETTE. Although I got this card years ago right around when I started the game, it sticks in my mind because of how many times I had to struggle against this NPC so early in the game.
Progenitrix - the final boss of Pharos Sirius Hard. Probably only a <5% drop rate. I had to run it over 30 times until it dropped. Very tedious to grind this, even unsynced.
Gogo, Master of Mimicry - you literally have to do all of Blue Mage quests/carnivale up to Endwalker to get this card. That being said, by forcing me to do Blue Mage, I discovered that Blue Mage is actually pretty awesome and really fun.
Every card trapped behind beast tribes - good god these were AWFUL to get through, especially the older beast tribe quests. Wow, I LOOOOVE wasting my time flying back and forth across the enormous Heavensward maps. If you ever see these cards available in a Mogtome event I highly recommend grabbing them so you don't have to suffer!!
Every Gold Saucer card - There's no way to grind these. You just have to do Gold Saucer stuff every week. You can do Lord of Verminion and chocobo races to speed it up, but then you're doing Lord of Verminion and chocobo races.
