'Doubly' in the Bible

“Woe to you, [self-righteous] scribes and Pharisees, hypocrites, because you travel over sea and land to make a single proselyte (convert to Judaism), and when he becomes a convert, you make him twice as much a son of hell as you are.

The elders who perform their leadership duties well are to be considered worthy of double honor (financial support), especially those who work hard at preaching and teaching [the word of God concerning eternal salvation through Christ].

These men are hidden reefs [elements of great danger to others] in your love feasts when they feast together with you without fear, looking after [only] themselves; [they are like] clouds without water, swept along by the winds; autumn trees without fruit, doubly dead, uprooted and lifeless;