This is harder to answer than it seems at first glance because many of the characteristics of criminal actions are similar to those of actions that are torts. However, we can identify at least two characteristics that should differentiate the two.
One characteristic that I believe should be present in any criminal act is intent. A person should not be liable to criminal punishment unless they, in some way, intended to do the illegal act. This is different with torts because an act that one party does or neglects to do can cause significant damage to a second party.
Another characteristic is violence. Violent acts should always come under criminal law. Such acts tend to damage the bonds of society much more seriously than torts do. Part of the point of criminal law is to reinforce the idea that such acts are dangerous to society as a whole and must be treated as such.
"Criminalization" of an offense simply means it is a JAILABLE offense.
In my state, Ohio, we have DEcriminalized the possession of Pot if it is under 100 grams, local ordinance does not have to abide by this though and can still criminalize it.
Possession is a Minor Misdemeanor punishable by up to $150.00 fine, no JAIL and no criminal record is a result of a convition.
The theory behind it was that such a small personal use of the drug is not a reason to fill the jails up with so called "criminals".
When a law/Oridinance is punishable by a money fine only, the "detriment" to society for not criminalizing it is minimal.
Is someone to be labeled a "criminal" for running a stop sign? This is the reason why traffic offenses are mainly lower degree offenses, of course state specific.
If no accident was caused, then the degree of "harm/injury" to Society is of little consequence if a stop sign was run through.