Who is the Imam of the Sunnis?

The title "Imam of Ahl al-Sunnah" is bestowed upon Imam Ahmad ibn Hanbal after his tribulation and his refusal to assent to the doctrine of the createdness of the Quran, and his steadfastness until Allah manifested the truth through him. This title is also used by some to refer to Abu al-Hasan al-Ash'ari.