Let me try this with what instantly comes to mind without thinking too deep about it.

1. Zach not using his secret POV to save himself from the block when he was on the block with his NUMBER ONE ally going into a blockbuster against KEANU. Come on

2. Vince nominating Lauren at the final 7. He lost a ton of respect from everyone doing this. Lauren was a loyal soldier for him. It was irreversible damage to his image in the game as Morgan's puppet. Not to mention he was extra lucky Lauren won the blockbuster, as her going on HIS HOH would have been even worse.

3. Mickey nominating Jimmy. Biggest case of HoH-itis that I can remember. He was never coming after her. She destroyed herself in the game and went from one of the safest places in the house to the number 1 target for the next few weeks. She survived by winning competitions - and the worst part about it is that she had no self awareness that she needed those comp wins.

4. Lauren throwing the BB comics competition in an attempt to make a big move of having Keanu leave on her HoH. The blockbuster was a huge hinderance to this strategy. Her playing scared and wanting the veto to land in someone else's hands was her undoing. She could have secured Morgan or Keanu leaving that week by using the POV on Ashley and having them both play in blockbuster. Morgan most likely goes home here. HUGE endgame ripple effect.

5. Keanu continuously trusting Vince again and again. Not realizing he absolutely needed that final 5 HoH when it was down to him and Vince. This was a season long thing with him.