Anything I've thought of so far always ends in "and then the underpaid delivery guy gets fired and starves to death" or "and then the person packing the boxes has their wages cut"
Are there methods here that actually just harm the COMPANY not the people who happen to work there?
The easiest way is to never buy anything from them, and encourage others to never buy anything from them whenever possible.
It's easier to shit-talk them from a consumer standpoint than an overt lefty one - it's not actually any cheaper, product quality is always shitty, would rather buy local, packages are constantly lost, if I'm so desperate for coffee filters or whatever it's easier I'll just go get it myself from a shop than have it shipped overnight - all of which are true and fair. People have this idea that "oh but it's so easy/cheap/convenient" but that isn't always necessarily (or even usually) the case, and it's worth reminding them whenever it comes up - especially since it always comes up when people are kvetching about a delivery gone wrong