Every plot point being addressed/solved
Kali being "adopted" into the Byers-Hopper family
Kali having her awesome style back
Kali and El/Jane having fun with kids (with their powers)
Kali and El/Jane getting waffles
El/Jane having a normal life, awesome friends and family, no boyfriend, cool wardrobe she likes
El/Jane and Max friendship coming back
El/Jane discovering queerness
El/Jane, Will and Jonathan being siblings
Joyce showing affection to Jonathan
Jonahthan and Will bonding
Medical injuries actually mattering (Max, Karen, Ted...) and having consequences
Every character having their personal arc resolved without relying on romantic plots
Vickie and Robin being cute together and having their date at Enzo's
Dustin talking to the party about the guys who beated him up
Dustin, Lucas, and Mike showing genuine yet casual support to Will multiple times
Argyle, Suzie, Max's mom and many others coming back
Jonathan and Steve kissing
Nancy, Holly and Mike being siblings
Erica and Lucas being siblings
Erica being more than smart and funny/sarcastic