Yet I have written you quite boldly on some points to remind you of them again, because of the grace God gave me (NIV)
Still on some points I have written to you the more boldly and unreservedly by way of reminder. [I have done so] because of the grace (the unmerited favor) bestowed on me by God (AMP)
Nevertheless, brethren, I have written the more boldly unto you in some sort, as putting you in mind, because of the grace that is given to me of God, (KJV)