Finally (του λοιπου). Genitive case, "in respect of the rest," like Galatians 6:17. D G K L P have the accusative το λοιπον (as for the rest) like 2. Thessalonians 3:1; Philippians 3:1; Philippians 4:8.

Be strong in the Lord (ενδυναμουσθε εν κυριω). A late word in LXX and N.T. (Acts 9:22; Romans 4:20; Philippians 4:13), present passive imperative of ενδυναμοω, from εν and δυναμις, to empower. See Ephesians 1:10 for "in the strength of his might." Not a hendiadys.