One of the worst ones I can remember was on Hollyoaks back in the Teens era, when the 6th form burnt down (2012?).
There was all this hype from Emma Smithwick, and all that happened was Tilly fell off a bookshelf and bonked her head, and Heroine Bitch Maddie fought her way through a whiff of digital smoke and dragged her out.
Honestly the crappest thing ever.
The best I can remember - I'm going to cheat and say the moment in Hollyoaks Later when Brendan got blown up on the beach. Awesome.
Also the car crash that killed Gennie in Emmerdale.
Not just great stunts, either of them, but also really good storylines about characters I cared about.
eta: Oh, and how could I forget Donna going off the roof in ED?

Though that was less of a disaster, more a dramatic moment.