First appearance (as Mr. Zero):Batman#121 (Feb 1959)
Victor Fries was a child who was fascinated with freezing animals: bugs, little critters, everything. His father got so fed up, he shipped him off to a strict boarding school. Well, Victor, despite his nerdiness, managed to meet Nora, an attractive girl.
Unfortunately, though Victor turned out pretty normal, Nora got sick, and was dying from some disease. And Victor couldn't stand to lose her. So he took on a job working for a large company, working on cryogenics. Now, Victor hated business, but he needed the money to help Nora.
As fate would have it, Victor discovered a way to freeze Nora, until a cure could be found. But Victor's boss, after shutting down the project, became angry, and came to stop the experiment. Victor fired a security guards gun, blowing holes in some coolant pipes, and as a result, Victor became exposed to the coolant. This had the strange effect of lowering his body temperature, but he survived. As a result, Victor had to wear a special refrigerating suit, too keep him cool. And thus, Mr. Freeze was born.
Mr. Freeze's crimes tend to involve freezing everyone and everything he runs into. Rather nasty, and pointless, actions, except they seem to satisfy his urge to get even with a hard, cruel world.