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Massive coronal ejection, I would say not likely.
Anything close to that it hasn't done at least since life began, if ever at all.
http://en.wikipedia.org/wiki/1859_solar_superstorm
Largest one in recorded history, that can disrupt radio and cause a black out. TV and commercial radio would still work.
The chances of getting hit by a astroid.
And there's more reasons to fear a Gamma ray burst.
You can see a CME comming(Not with the naked eye) takes normally 4 days, fastest 18 hours with a cleared pathway. A gamma ray burst would travell at the speed of light and kill mostly everyone.
Now that I think about it though, I doubt that the sun could produce a CME strong enough to permanently damage our atmosphere.
The answer to all this is the Earth's gravitational field. Imagine it the Earth's Core emitting it's gravity in such a way that it acts like a force field. Infact, here's a model (courtesy of Astro.wise.edu and google), the green lines being the field. Because of that barrier the earth doesn't get pelted with cosmic rays of suck and death.
As you seen in the post above the sun has gotten pretty violent with us in the past, but we believe that field protects us pretty well. Hell, while it was young it probably has ejected something powerful while the Earth still stood.
Considering the lack of past flares which were great enough to fry half the Earth, as well as the Earth's magnetic field which can protect us from cosmic rays and solar wind, I find such a flare to be very highly unlikely to manifest anytime soon.
