Tax Court Cases
I did a retrospective study of my own tax court cases in April of 2018. This is only for cases which were decided on the merits; it doesn't include cases where the client withdrew or the case was transferred or consolidated.
Of course, most cases don't even require going to tax court; most of them get resolved within the IRS. This list only represents about 10% of the tax disputes I've handled, but it nonetheless gives an idea of what to expect. As you can see, tax disputes usually end in some kind of settlement.