Wlad-Fury was probably the worst fight ever televised. They both should have been suspended for life afterwards.
The heavyweight title fights that are terrible stand out because heavyweight title fights tend to be good, and even if they aren't competitive, usually entertaining. The bad ones tend to be infamous. But I'd say the worst title fight ever could've been any of the thousands of lighter-weight title fights (below Welterweight) that I got suckered in to watching and totally forgot about within minutes of watching them. There are a TON of bad lighter-weight fights. TONS. Like, where neither guy hits hard enough to stop the other, and it's just tedious rounds after rounds of nothing much happening for the better part of an hour. Far too many divisions within a couple three pounds of each other with too many garbage champs over the last 40 years or so to even keep track of which of those champs made the worst title defense.
Recently was Joshua v Parker. Referee executed a criminal protection job by breaking them apart anytime Parker got inside or even remotely close to that fragile, industrial cardboard grade chin Joshua has. That referee should be on a watch list.
Wlad/Fury was pretty bad. I'm sure they're worse fights out there, but the fight did not live up to my expectations.
I'm sure most would rewatch Joshua-Parker on a loop rather than rewatch any Tevin Farmer successful 12-round title defense. Or maybe cue up Maurice Hooker's defense against Mikkel "Slikk Mikk" LesPierre ... huh? I dare you. Another classic. You don't find a lot of people "bumping" old Hooker-LesPierre threads to argue the merits of that one. So many of those "title" fights just disappear without leaving much of a trace. Utterly forgettable.