Adverbial form meaning far more, much more, to an even greater degree. Paul uses it of his labors exceeding those of other apostles.
Paul's repeated use of superlatives about his ministry reveals not boasting but testimony to grace. He suffered 'far more' imprisonments, beatings, and dangers (2 Corinthians 11:23). Yet his joy was also 'far more' abundant. Suffering and joy are not opposites in God's economy — they are companions.