17. Anakin Is Assigned To Protect Padme - Attack Of The Clones
In their infinite wisdom as dudes in charge of managing the galaxy's direction, the Jedi Council sure do know how to make daft decisions. Although many of them are gifted with the handy talent of foresight, they all blatantly cannot see that assigning Anakin Skywalker to protect a young, attractive female will have consequences. They're both in their late teens at this point, with emotions running high. Although Anakin, as a sworn Jedi, has renounced love and marriage for reasons (coz attachment leads to the dark side and all that), he pretty much instantly chucks these out of the window when Padme starts making the moves. This is a particularly bad decision on the council's part as not only does it cause one of their most promising students to declare a big eff you to the teachings, but this ultimately leads to a Padme pregnancy, Anakin's crazy visions of her dying and his fall to the dark side. All you had to do was send the aptly-named Jedi-Not-Appearing-In-This-Film!
16. Jar Jar Purposely Gives Palpatine Even More Power - Attack Of The Clones
If it's not bad enough that some hapless idiot decided to give Jar Jar Binks, a bungling Gungan who is about as useful as a chocolate fire guard, actual powers in the Galaxy's council, he truly proves his ineptability by lobbying for Senator Palpatine to be given complete control over basically everything, including the newly-discovered clone army stumbled on by Obi-Wan. Not only does this allow Palpatine - who is secretly pulling the strings behind practically everything - the tools to bring about the Jedi's downfall, but it also ultimately leads to Palpatine having the means to control an entire army whenever he so chooses. He ultimately enforces this power during Revenge Of The Sith when the clone army is reprogrammed using order 66. Lesson here - never give power to a comedy character.