Some silly decisions from Hopper - going in the tunnels alone in the dead of night.
Dustin after all his 'respect for the rules' he keeps a big ass secret from the group - totally out of character.
Max's step-brother, not sure what was going on there, was building to him either finding out and helping (but that would have been too similar as what happened to Steve) or him taking in the evil spirit and becoming a nemesis or something. But that arc faded to nothing in this series.
And especially loved some of the 80's references, Sean Astin, Paul Reiser, ET, Aliens, The Thing, Gremlins, Goonies....................so much!
Bust still been some of the best TV on atm.