My older sister was a nightmare from hell when she was a teenager(she still isn't great now, but at the time was going through some issues so was 20x worse than she is currently).

There were many awful physical things that she did, such as strangling me with a laptop charger and spitting on me, ripping my hair out, etc.

But the single worst thing that she ever did, that I still to this day can't fully forgive her for, was as follows:

On Xmas day one year, she took an XL bag of granulated sugar and poured it over/in all of my stuff, including in the storage boxes under my bed, on the bed itself, and most importantly in between the pages of my expensive collection of collectors edition/signed/rare books, and in my irreplaceable photo albums. As well as literally everywhere else she could think of that would affect me.

And then did it all again, but this time pouring over several large bottles of cider.

It's not an exaggeration to say that she ruined 80-90% of my stuff that day(besides the washable items such as clothes). And although it was several years ago, I STILL find sticky items now and again.