For me, it has to be Jedi Rocks. Having watched the 2004 DVDs as a child, nothing particularly is too egregious, but every time Jedi Rocks comes on while I’m watching with my family, I feel really uncomfortable. It’s just stupid. They should at least add subtitles.
Before despecialized, I’d be embarrassed at the point of Jedi Rocks if I was showing the trilogy to someone who wasn’t a “fan.” There are worse changes, but this one illicits a unique response for me.