Correction, Komodos have venom. There are no special bacteria in their saliva, that was just a theory with no actual evidence behind it. Their venom is an anticoagulant, so the wound stays open and bleeding, and when the bitten animal goes and wallows in one of the many crap filled watering holes on those islands.... You can see how an infection starts.
That being said, a large Saltwater Crocodile could easily take down a large Komodo Dragon, simply because it would be so much bigger. Of course, the two species most likely come into contact with each other very rarely if at all, and neither would view the other as an easy meal, so I don't see why they would be fighting in the first place..