This is an important title for God. (See: [[rc://en/ta/man/translate/guidelines-sonofgodprinciples]])
# full of grace
"full of kind acts towards us which we do not deserve"
# He who comes after me
John is speaking about Jesus. The phrase "comes after me" means that John's ministry has already started and Jesus' ministry will start later, after John's.
Be careful not to translate this in a way that suggests that Jesus is more important just because he is older than John in human years. Jesus is greater and more important than John because he is God the Son, who has always been alive.