Who wrote 2 John:

The author of 2 John identifies himself as The Elder (2 John 1:1). This title was a common title given to the Apostle John and has never been attributed to anyone else. The writing style, theology, and Christology of 2 John is consistent with 1 and 3 John, and The Gospel According to John, all written by the Apostle John.

Nearly all scholars agree the Apostle John is the author of 2 John. No good reason has been presented to believe otherwise and no alternative authors have been proposed.