Loudest were, just, Dragster at the Motorheadbangers party at the Ritz in Manchester, around ‘83-ish. It was like being run over by, strangely enough, a Dragster. 😉
Close behind were Spider at JRs in Blackpool. The sound was also absolutely terrible, the PA pushed well beyond its limits, so that was the most painful. And they were utterly dreadful too.
After that, probably Motorhead at various venues, all of which were considerably bigger than the above, which is probably why they aren’t first. I remember sticking my head in the bass bins at Queen’s Hall, Leeds. Intense. 😂
One other that springs to mind for different reasons was the bass drum, Iron Maiden, possibly Powerslave, at Manchester. I’d eaten just before going in and after 20 minutes the ludicrous bass drum impact had me feeling sick as a dog.