Paul spreads the gospel, particularly to the Gentiles, through his suffering. That is the summation of Thom Schreiner’s chpater on “Suffering & the Pauline Mission.”
Paul was attacked for his suffering: accused of being a vacillator, criticized for his lack of success in evangelism, told he needed letters of recommendation, charged with hypocrisy and attacked for his failure to take pay for his work (88).
Schreiner does not see the Corinthian letter as a battle between he, his apostleship and the Corinthians [I was not convinced] (91).
“. . . his sufferings do not disqualify him from his apostolic office but are the means by which God’s Spirit is poured out in the lives of his converts” (95).
Regarding the enigmatic verse in Col 1:24 about Paul filling up what is lacking in Christ’s suffering:
“The ‘filling up’ of Christ’s afflictions is the pathway by which the gospel is ‘fulfilled’ in the lives of the Gentiles” (102).
“Paul through his sufferings, however, extends the message of Christ’s all-sufficient death to the Gentiles, for such a message was concealed from the Gentiles during the life of Jesus of Nazareth. . . . What is lacking in Christ’s afflictions is that the benefit of those afflictions had not yet been proclaimed among the Gentiles. . . . Paul’s sufferings, in other words, are corollary of Christ’s . . . Paul’s sufferings mirror and reflect what Christ has done, so that the messenger in this sense replicates the life of the one proclaimed” (102).