Don't know if it is still around but: Iron City.
It's still around, but it's outsold by IC Light these days. And I don't think "Ahrn" its as bad these days as its rep.
I have to go back for the 70s for these, but our "cheap supermarket beer" was Weidemann's. A typical house party would feature a case of the "good stuff" (Bud, lol), and 2-3 cases of Weide's. But there were even worse beers we couldn't stomach... Falstaff, Carling Black Label, Red White & Blue. Back then we considered Tuborg a premium import.
But the all time worst "cheap" beer was Canadian Ace. It only came in clear half gallon bottles. In 1978 or so it was $0.99.
However, the single worst beer I ever had in my life was at Ye Olde Bar and Beer Can Museum in Northampton, MA. It was from either Zimbabwe or Swaziland and came in a series of cans featuring African animals. It was a cloudy lager, like a goat with a urinary infection took a piss.
FWIW, I had a sample of a really vile nitro microbrew chocolate stout couple nights ago. Forgot the brewery though.