By that I mean what is capable of cutting through the greatest variety of materials? Is it surgical steel? A Samurai sword? Obsidan? Some kind of laser? A roll of oven-melted-than cooled plastic wrap?
Water.
Or hydrogen. Bonds with a great many things to form variations on the theme of acid.
Probably doesn’t count, but maybe thermite?
In a three way showdown I think I could take the guy with the vial of acid, 
but would hesitate approaching the guy with the soild rocket booster. :eek:
Nothing is sharper and colder than when a woman really rejects you. 
Obsidian. Keeps its edge to a thickness of one molecule. It is sharper than any metal blade could be made to be.
A laser, since it can cut diamond, the hardest mineral?
Or, maybe, a thankless child?
I’ve had some diamond-cutter erections.
The metal tip on a scanning probe microscope, which is often a single metal atom like the final cannonball on one of those pyramid piles. They do use these tips to move bits of sample around - it’s as much “cutting” as anything else you could call it.
Why can’t metal blades have single-atom tips?
IIRC, it is because of the way that the molecules are arranged, you might be able to make one that thin, but the edge wouldn’t keep after use.
This is General Questions.
I would go with the water for its ability to cut the largest selections of material. Other runners up would be lasers, and ultrasonics.
Well, if you are going in include that, why stop at puny chemical explosions? 
IRRC one of the Operation Plowshare plans involved using a series of nuclear bombs to cut a sea level canal between the Atlantic and Pacific oceans.
Boron carbide.
The most abrasive substance known, and damn near as hard as diamond. A cutting wheel surfaced with boron carbide will cut through damn near anything. You might need to replace the wheel a few times to cut through a diamond.
The dust at the bottom will be about 46% diamond dust and 54% boron carbide dust.
Diamond are split if large and small diamonds may be cut with a wet diamond saw. Diamonds are finished wet with diamond dust on a metal lap wheel.
Re: OP IMHO there is NO one general purpose cutting agent/tool for the wide range of material existing today. What works well for one may be very poor with another.