This is the way.

There is a video from the lock pick lawyer where he receives a padlock in the mail with so much tape that it takes him whole minutes to unpack.

Concrete is nice, other options are piles of soil or brick in front of the door. There probably is a sweet spot where enough concrete slows down an excavator and enough bricks mixed in the soil slows down the shovel. Extra points if there is no place nearby to dump the rubble.