Mmm...Banishment.
Reaching absolute zero in our universe is a physical impossibility because of Maxwell's Demon aka the Second Law of Thermodynamics, which dictates that energy moves from higher concentrations to lower concentrations -- it is, after all, basically the vibration and movements of molecules. If you kick a soccer ball into a stationary soccer ball, the momentum will balance out. Therefore, a spell that actually has a target reach absolute zero would have to travel to a place imbued with a complete lack of energy -- some kind of dimensional limbo. In essence, they would be cast off into their own miniature universe. Now, you could go to all the trouble of learning how to do that...or you could pick up a heavy blaster cannon and fry their ass. Which one's more convenient?
Actually, the cannon isn't always. If you need to focus your attack on one particular target, such as in a situation where, say, you're right next to a nuclear reactor and your big gun could accidentally hit it and blow both them and you sky-high, you don't want something that's "as clumsy or random as a blaster." Cold attacks of the nature depicted in Chrono universe magic would require extraplanar phenomena to occur to sap energy from a target and direct it somewhere where it would not normally go, but the same sorts of phenomena would have to occur in order for energy to concentrate in an unusual manner at the expense of everything else in the vicinity, as it does in fire attacks. Indeed, unexplainable phenomena are responsible for people being able to do this stuff in the first place. We know from Chrono Cross that even if the Law of Conservation of Energy holds true at every possible level, the Chrono omniverse does not require that each universe within its structure is a closed system unto itself -- the omniverse collectively would be a closed system. Energy could perhaps be directed into another plane of existence, or a sub-universe similar to subspace.
The sun's temperature is over 10,000 degrees Kelvin, due to the high-energy molecular reactions required to sustain the functionality of the flaming plasmatic mass it's composed of. So, yeah, I'd believe that.
I tend to favor the CC system of Fire, Cold, Earth, Wind, Shadow, Holy, and the Chrono Cross, which has yet to be truly named or even classified. (Note the Cold moniker for blue attacks -- it encompasses both ice and water, and it just works for me somehow. Ah, well) Within this system, the first four can be semi-rationalized -- the universe's laws still hold, despite the unnatural mechanisms used to employ its energy, but nearly every facet of the latter two (three, really, but the Cross, as I said, hasn't been properly explained in terms of what energies it employs) seems to scream out "Physics can bite my ass!!" Sending enemies to hell, removing their souls from their bodies, exploding stars and only hurting the bad guys, creating singularities that don't destroy the planet, summoning armies of angels whose blasts heal the party but damage the aggressor, calling asteroids down from space without killing everything within a hundred miles...uhhh, yeah, those are really shining examples of adhering to physics.
[sarcastic face]
But seriously, that's kind of the point -- being able to transcend to the highest level of existence and manipulate the mind and the laws of the universe itself. According to Schala, the universe itself is sentient and therefore can control some of the mechanisms of its makeup, as can all sentient beings. It has its own natural growth, as well, that it would not disturb. Effectively, magic of a physics-defying caliber is the very mind of God.
Question: Are Leebot's lists the official ones, or just ideas? I'm guessing that Fire, Cold, Lightning, and Shadow are the elemental innate spells, and that there are other categories such as temporal spells, necromancy, etc. I haven't had time to really read this -- I've been in St. Louis for the past four days at a band contest.