Exceedingly (huperekperissou). Double compound adverb, only in 1Th 3:10; 1Th 5:13 (some MSS. ̇ōs). Like piling Ossa on Pelion, perissōs, abundantly, ek perissou, out of bounds, huperekperissou, more than out of bounds (overflowing all bounds).
And perfect (kai katartisai). First aorist active articular infinitive of purpose (eis to ideiṅ̇kai) of katartizō, to mend nets (Mat 4:21) or men (Gal 6:1) repair. Chiefly late.
That which is lacking in (ta husterēmata). The shortcomings, the lacks or left-overs (Col 1:24). From hustereō (husteron), to be late.