These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Ass Pull: True, Eddy's brother's sociopathic nature was foreshadowed a few times in the original show, but the ending feels like this to some. All of the damage Eddy took was all of a sudden Played for Drama, and kids instantly forgive and befriend the Eds afterwards.
Author's Saving Throw: The movie addresses a few complaints about the show: Kevin and Sarah getting hit by karma, Kankers helping the Eds for once, Eddy apologizing for his actions and Eds becoming accepted by the community.
Misaimed Fandom: Some people enjoyed Eddy getting beaten by his brother because of the quicksand prank.
Moral Event Horizon: Eddy's Brother crosses it when he begins to hurt Eddy, and then admits freely that he's always done this to him.
One-Scene Wonder: Eddy's brother who only appears in the last five minutes of the movie yet leaves a huge impression.
Rescued from the Scrappy Heap: Kankers try to help the Eds and are noticeably disgusted and terrified when Eddy and Edd get beaten by you-know-who. Contrast this with Fistful of Ed, when they weren't above abusing curb-stomped Double D. Contrast this with everything else related to them.
Sarah and Kevin's Karma Houdini Warranty expires and, at the end, finally accept the Eds. Kevin even offers them some of his jawbreakers.