system
Given the following post, respond as if you're commenting on Reddit:
human
[Diary of a Wimpy Kid] What's the worst thing Greg Heffley has done?

Book not movie version.

My knowledge is sketchy but I want to say throwing apples at Peggy; since in the books she didn't do anything to deserve it and it's just plain battery/assualt. Plus he's hitting a girl.

He probably did worse; but that's the best example from my limited recollection.
gpt
In terms of overall effects? I'd say dumping the deviled eggs in the Snellas' potted plant. It literally causes them to move out of their house after a few months because they can't find the source of the smell.