I don’t collect sets, but I do have three complete ones: Japanese Vending Series 3 (Green); Japanese Southern Island mini set (all still sealed); and the non-TCG Bandai Carddass set (series 2 + 3). Bought all three of those as a full set.
I also have two sets almost complete: Japanese EX Battle Boost (only missing 3 cards apparently) and Korean Fairy Rise (only missing 4 Secret Rare cards apparently). I think I opened four Korean Fairy Rise boxes, and still have two sealed ones somewhere in my room. 
I used to collect Mimikyu in all languages and this set contained three Mimikyu cards (1 Ultra, 1 Secret, and 1 Hyper Secret). Although I think I ended up buying the Hyper Secret as single at the time.
I knew @pokesoap was a pretty big set collector who had 25+ sets completed, but I think she stopped collecting 1.5 years ago.
Here is a similar thread from the start of 2018 for those interested.
Greetz,
Quuador