The word agony refers to a paralyzing or painful experience. The English word is derived from the Greek a- "without" + gon "side" (cf. "an agony of indecision").
In Christian contexts, agony usually refers to the pain of Jesus on the Cross, particularly the spear-thrust into his side. Even while Jesus was being taken down from the cross, his agony would have been excruciating.
Modern medicine has developed painkilling drugs which are effective against agony, so that it is rarely seen in Western countries today.