As far as Jesus of Nazareth existing, there's no respectable historical scholar that will dispute he lived, had some sort of following, and was crucified.
Was he God or not, well of course that's up for debate and what not. But there is not one scholar who would dispute that he actually lived, actually had a religious following of some sort (how large is debateable), and that he was crucified.
One can ascertain this by extra-Biblical sources, no need to even debate the Christian Scriptures to know this.