this is the Greek word that there was translated 'destroy'
Strong's Concordance
katargeó: to render inoperative, abolish
Original Word: καταργέω
Part of Speech: Verb
Transliteration: katargeó
Phonetic Spelling: (kat-arg-eh'-o)
Definition: to render inoperative, abolish
Usage: (a) I make idle (inactive), make of no effect, annul, abolish, bring to naught, (b) I discharge, sever, separate from.
HELPS Word-studies
2673 katargéō (from 2596 /katá, "down to a point," intensifying 691 /argéō, "inactive, idle") – properly, idle down, rendering something inert ("completely inoperative"); i.e. being of no effect (totally without force, completely brought down); done away with, cause to cease and therefore abolish; make invalid, abrogate (bring to nought); "to make idle or inactive" (so also in Euripides, Phoen., 753, Abbott-Smith).
["2673 (katargéō) means 'to make completely inoperative' or 'to put out of use,' according to TDNT (1.453)" (J. Rodman Williams, Renewal Theology "God, the World & Redemption," 389).]
it does not mean 'annihilate'
it means he will be rendered powerless.
it's right there in the context:
God will through death render powerless him who had the power of death