That scene when Hopper yells at Eleven
I've always liked Hopper but that scene after Eleven comes back after sneaking out where he just lashed out at her, screaming, cutting off the only connection she had to Mike, was the first time i really disliked him. Hopper was completely in the wrong and acting like a lunatic, seeing El ball up in the corner crying as he was screaming was awful to watch, felt so bad for her there.
I know Hopper admits it later on he was wrong but he should have realized it in that moment, i don't know how he thought acting that way was gonna do any good. Nevermind the fact that she could destroy the entire cabin and Hopper with the blink of an eye if made angry enough.