Who gives the most accurate credit score?

I don’t think that there is such a thing as “most accurate”. Each of the credit companies (Equifax, Trans Union, etc.) has their own proprietary algorithms which take into account slightly different factors, based on their assessments of what’s important.

Even the FICO people (the original credit score people) have different FICO scores depending on the exact needs of the companies buying their services.

So each score is accurate in itself but you cannot really say one is right and the other wrong, because they’re calculated differently.

Accuracy is a matter of interpretation. For all practical purposes (mortgage, credit cards, apartment rental, etc.), I have found that the only credit score that matters is the FICO score.
Is it accurate? That depends on whether there are any errors in your file.

There are three credit reporting agencies. There are also different credit scores for different things. You can check your credit history free at each of the three reporting agencies once a year.