Which Horonite, along with Tobiah the Ammonite, opposed Nehemiah's work?

Answer: Sanballat

Sanballat the Horonite and Tobiah the Ammonite official were disturbed by Nehemiah's arrival and mocked the rebuilding.

“But when Sanballat the Horonite and Tobiah the Ammonite official heard about this, they were deeply disturbed that someone had come to seek the well-being of the Israelites.”— Nehemiah 2:10 (BSB)