Contest; wrestling; severe struggling with pain and suffering. Anguish is the reflection on evil that is already past, while agony is a struggle with evil at the time present. It is only used in the New Testament by (Luke 22:44) to describe our Lord's fearful struggle in Gethsemane.
The verb from which the noun "agony" is derived is used to denote an earnest endeavour or striving, as "Strive [agonize] to enter" (Luke 13:24); "Then would my servants fight" [agonize] (John 18:36). Compare 1 Corinthians 9:25; Colossians 1:29; 4:12; 1 Timothy 6:12; 2Tim 4:7, where the words "striveth," "labour," "conflict," "fight," are the renderings of the same Greek verb.
These dictionary topics are from M.G. Easton M.A., D.D., Illustrated Bible Dictionary, Third Edition, published by Thomas Nelson, 1897. Public Domain, copy freely.
Easton, Matthew George. "Entry for 'Agony'". "Easton's Bible Dictionary".