As much as I loathed Hunter/Orton, that actually approached mediocre all around. The context is what pushes it into the "all-time worst" category.
Absolute worst has to be between Hogan/Sid, the Bret/Yokozuna/Hogan debacle and Cena/Miz. No redeeming qualities at all within those three, and two had DQ finishes. Admittedly, one was a fakeout, but seriously?
Everything else either had a celebrity in it or was merely crap. Not the worst ever.
Sidenote: Is Triple H the worst WM main event worker ever? Nothing but crap comes up when you think of Hunter and WM main events. I wouldn't say that he was ever in the worst ever WM main event, but out of 6 tries, he's had admittedly one classic match (WM XX), one decent match aided by great atmosphere (WM 22) and 4 mediocre to awful matches. Sid might be the only one worse with multiple matches under his belt (2, both mediocre to awful). Hogan had 2 bonafide awful main events (WM 2 and WM VIII), but everything else but his WM VII match were either really good matches or outright genre benchmarks.
Other than those 2, NO other worker has multiple bombs like Hunter has had in the WM main event.