If you want maximum temperature you could look at massive bodies such as Neutron stars or white dwarves which have high pressures.
When you look at such things as blackholes I don't think you have pressure- though I don't know if anyone knows or can know.

Stars collapse because they lose energy. A large star within few million years runs out fuel and then collapses.
It seems unlikely in nature to find stars that make Antares
look small- but there should be freak occurrences at some time within the vast universe.

Google search, Largest star in universe:

"I contacted Roberta Humphreys from the University of Minnesota, the researcher who calculated the size of VY Canis Majoris, and posed this question to her. She noted that the largest stars are the coolest. So even though Eta Carinae is the most luminous star we know of, it's extremely hot - 25,000 Kelvin - and so only a mere 400 solar radii.

The largest stars will be the cool supergiants. For example, VY Canis Majoris is only 3,500 Kelvin. A really big star would be even cooler. At 3,000 Kelvin, a cool supergiant would be 2,600 times the size of the Sun.

That, she believes, is the largest possible star. "
http://www.universetoday.com/2008/04/06/what-is-the-biggest-star-in-the-universe/

Now suppose you had a star 3000 times the size the sun- and say surface temperature was cool, but it's interior temperature would be quite hot. The temperature would depend upon what elements are fusing and how fast the energy was conducting through the matter.

Hmm:

"In a neutron star the matter is in a state known as neutron-degenerate matter, with a more exotic form of degenerate matter, QCD matter, possibly present in the core."
http://en.wikipedia.org/wiki/Star
QCD matter:
"Quark matter or QCD matter (see QCD) refers to any of a number of theorized phases of matter whose degrees of freedom include quarks and gluons. These theoretical phases would occur at extremely high temperatures and densities, billions of times higher than can be produced in equilibrium in laboratories."

So, suppose you had iron core of a sun, pumped up with enormous amount of energy- without this energy to would collapse- that core temperature might have the highest temperature of normal matter- though it's no doubt have weird properties at such temperatures and pressure.

And with neutron star- it be more than large enough to turn into a black hole but is it's having enough energy pumped into it so it does collapse [yet] into a black hole- which would have highest temperatures of "non normal" matter.

Or to get enough energy you could have two neutron star colliding at near light speed- though I suppose it might simply turn it into a black hole.
So, then, at some speed less than this, that doesn't instantaneously create a black hole.