What was the real strength of the White Fang (Kakashi's father)? Was he good at taijutsu, nin, or any other jutsu?
According to his Naruto Wiki article, he was
...proficient in kenjutsu, his reputation as "Konoha's White Fang" stemming from his extensive use of the White Light Chakra Sabre, which emitted a streak of white chakra when swung.
The citation for this is Chapter 242, page 12.