Four. Rucka's is a pretty different guy from the others, too. You can probably guess which one I'm partial to. And then there's DCAU Vic, who has bits and pieces of each (except maybe Veitch). It's really kind of surprising how few writers have actually handled him over the last forty years. He did have an appearance in Steel, and played a part in L.A.W. but the guy has had relatively little coverage. But the fact that every writer who's handled him has treated him so differently is one of the things that makes him so intriguing, and in desperate need of a scans-analysis series. (But then, is it that Vic desperately needs analysis, or that I desperately need to analyze him?)
Course, there's also Moore's, if you want to consider Rorschach a take on Vic (i don't).