Complain to the previous poster that something he or she did or did not do has somehow inconvenienced you. Some examples:
I ordered a computer from you 2½ years ago. How come it hasn't shipped yet?
I bought an Xbox 360 from you this morning and it caught fire the moment I plugged it in. I demand a refund.
I got food poisoning from the food I ate at your restaurant last night.
Note that my examples assume that the previous poster operates some sort of business. The actual posts don't have to, but that's the best way I could think of to prevent confusion with Accuse the Person Above You of Crimes.
As usual, if you're confused, feel free to ask me about it.
Could you have refrained from dumping an entire bottle of sulfuric acid into his bowl before going to the bathroom? I ain't a miracle worker, you know...