How much of the Earth would a spoonful of the Sun scorch? How much of the Earth would a spoonful of the Sun scorch if held at ground level?
I basically would like to conceptualize the heat of the Sun on a smaller scale, please.
 A: Consider the core of the sun, which is stated on Wikipedia to have temperature around 15.7 million K, density 150 g/cm3. A teaspoon is 5cm3, so 750g.
How much power is this generating? Well, the sun generates 4 x 1026 W and the core of the sun (out to 25% of its radius of 7 x 108m) consists of about 2.2 x 1025m3 and does almost all the fusion. So perhaps surprisingly, the ongoing power output of a teaspoonful of the sun's core (sampled as a representation across the whole core) is very underwhelming, a tiny fraction of 1W. Wikipedia provides another estimate for the very centre of 276.5 watts/m3, which is still approximately nothing for a teaspoonful.
We can neglect the effect of fusion when transported to the surface of the earth -- quite aside from anything else it will stop once the pressure is removed, which will happen pretty quickly once released. This may also give a feel for why generating usable power by nuclear fusion is difficult.
What about the stored heat? I know approximately nothing about plasma physics, but it feels like 750g of stuff at 15.7 million K is going to scorch you at least as badly as 750kg of stuff at 15700K. A small, white-hot car isn't all that scary, but you wouldn't want one in your face. Neither is raising the temperature of a 750 tonne building by 15.7K going to trouble the planet as a whole, although you probably don't want to be in the building when it happens since the heating will be distinctly uneven. Maybe this dense plasma has thermal capacity orders of magnitude higher than a car or a building, I don't know.
But where's the kaboom? What happens when you take 750g of stuff at 265 billion bar and release it to atmospheric pressure (1 bar)? Again, this is plasma physics, gas laws may not apply, but as a first guess it would get 265 billion times bigger except that in the process it will presumably cool by a factor of (at least) 1000. It wants to occupy 1.3 million m3, divided by 1000, that is to say a cube 10m to a side full of gas that's still (by the standards of gases on the surface of the earth) very hot. Don't stand near it. Note that I'm in part double-counting the heat that I already talked about above.
Oh yes, and there's at least some chance that the hydrogen will combust in the presence of terrestrial oxygen. A tank of compressed hydrogen going off can't be all that much fun, but I've no idea how well our spoonful would mix with air compared to its rate of cooling.
I'm afraid that's as far as I can get, but I think it gives some idea that there will be a considerable explosion but no earth-shattering kaboom.
The surface of the sun is even less exciting in small volumes -- it's not very dense and its temperature is only about the same as that of a light bulb filament (because blackbody radiation of a given temperature has the same colour, geddit?). Any part of the sun is at least partially-ionized though, so I suppose at the very least it might fritz your phone.
Numbers cribbed from https://en.wikipedia.org/wiki/Solar_core
A: What part of the sun?  That would make a huge difference in your question.  Overall, these types of hypothetical questions are rather non-nonsensical without really defining the parameters very clearly.
That said, keep in mind, we have "released the power of the sun on the surface of the earth" a few times already.  Not only that, we have even contained it!  Granted, we are still in our infancy of this technology, so we are still figuring out a lot of the parameters and limitations we will face.
A: 10 million tons of neutrons burning at 15 million degrees it would be something similar to crater lake, ground zero would probably be glass, or a chunck of iron, at 15 million degrees it would instantly melt a city just with the flash. 1 teaspoon weighs 10 million tonnes(average mass of a star)it would be a textbook example of a nuclear event.
