Fox
For what its worth, the below study found the bias in Fox to be 3 points in the 2020 election, similar to the bias in most other major media polls in that election.
https://www.semanticscholar.org/paper/Shy-Trumpers-and-Live-Callers-%3A-An-Analysis-of-The-Thies/764d106e87be9e37df5a86835b64042c6962a9d3