If you want to take years to damage it, anything around 85dB for eight hours a day will do it. But this is likely to give you tinnitus and just make you hard of hearing at certain frequencies. For each 3dB increase you can roughly half the exposure time (so 88dB is 4 hours a day).
If you want to screw it a bit more, an exceptionally loud firework or similar explosion about 5 feet away may just be enough to permanently damage it, but again it may not be completely gone and may result in tinnitus. You may also suffer burns from the firework, as it will need to be a big one.
A one off sudden blast of anything over about 150dB will pretty much get the ear on the side that's exposed. This will be physically excruciatingly painful. But you'll probably be standing on something like an aircraft carrier deck next to a jet during take off, or adjacent to an exploding bomb; so it might not bother you…
I know you said you didn't want questions on your sanity… but what's so bad about the noise levels you're experiencing?
Instant total destruction of your hearing is actually quite hard to achieve by using sound sources - as I'm writing this I'm thinking some sort of nasty infection might have more luck…