The worst thing that we came home to wasn't technically vandalism, but we had hired someone to come over twice a day to let the dogs out, clean the cat boxes, bring in the mail, and newspapers, etc.
We came home, and yes, our mail and newspapers were inside. But DH's cousin lives two doors down from us and while we were gone, she had told DH's mom that we had a bunch of newspapers piling up in our yard, and didn't we know that was an invitation to theives...um yeah. That's why we HIRED someone to bring them in. Apparently she just showed up the night before we were to return and brought them all in. She also hadn't bothered to do anything with the pets. The dogs were in the kitchen, and we literally had to replace the floor after that. It was like a lake, an OCEAN of pee in there.

And the cat boxes were filled beyond capacity. It was SOOO gross!!
Just what we wanted after a long day of airplane travel. Finally to get home, exhausted and ready to go to bed, and then have to clean litter boxes and mop up urine.
As far as actual vandalism, some teenaged boys got drunk and decided it would be fun to go to a cemetary and destroy grave markers and headstones. They did $1600 damage to DH's ancestor's graves alone. Thankfully, they were caught, convicted, and ordered by the court to pay restitution, which they did. We had paid for the repairs ourselves (home owner's insurance doesn't cover your family's graves - we found that out) and people told us we'd never get that money back. It took several months, but we eventually did get the money. Sadly, one of the headstones could not be repaired (DH's great-great-great grandfather's ) and we had to have a replica made.