Ok, so back to 1 Corinthians 15:26, The last enemy that shall be destroyed is death. I think I might have misunderstood you, I thought you were saying this verse is talking about the second death. This verse is talking about the first (physical) death, right?
1Co 15:1 Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand;
1Co 15:2 By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain.
1Co 15:3 For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;
1Co 15:4 And that he was buried, and that he rose again the third day according to the scriptures:
1Co 15:5 And that he was seen of Cephas, then of the twelve:
1Co 15:6 After that, he was seen of above five hundred brethren at once; of whom the greater part remain unto this present, but some are fallen asleep.
1Co 15:7 After that, he was seen of James; then of all the apostles.
1Co 15:8 And last of all he was seen of me also, as of one born out of due time.
1Co 15:9 For I am the least of the apostles, that am not meet to be called an apostle, because I persecuted the church of God.
1Co 15:10 But by the grace of God I am what I am: and his grace which was bestowed upon me was not in vain; but I laboured more abundantly than they all: yet not I, but the grace of God which was with me.
1Co 15:11 Therefore whether it were I or they, so we preach, and so ye believed.
The Resurrection of the Dead
1Co 15:12 Now if Christ be preached that he rose from the dead, how say some among you that there is no resurrection of the dead?
1Co 15:13 But if there be no resurrection of the dead, then is Christ not risen:
1Co 15:14 And if Christ be not risen, then is our preaching vain, and your faith is also vain.
1Co 15:15 Yea, and we are found false witnesses of God; because we have testified of God that he raised up Christ: whom he raised not up, if so be that the dead rise not.
1Co 15:16 For if the dead rise not, then is not Christ raised:
1Co 15:17 And if Christ be not raised, your faith is vain; ye are yet in your sins.
1Co 15:18 Then they also which are fallen asleep in Christ are perished.
1Co 15:19 If in this life only we have hope in Christ, we are of all men most miserable.
1Co 15:20 But now is Christ risen from the dead, and become the firstfruits of them that slept.
1Co 15:21 For since by man came death, by man came also the resurrection of the dead.
1Co 15:22 For as in Adam all die, even so in Christ shall all be made alive.
1Co 15:23 But every man in his own order: Christ the firstfruits; afterward they that are Christ's at his coming.
1Co 15:24
Then cometh the end, when he shall have delivered up the kingdom to God, even the Father; when he shall have put down all rule and all authority and power.
1Co 15:25 For he must reign, till he hath put all enemies under his feet.
1Co 15:26
The last enemy that shall be destroyed is death.
Seems the context and timeframe is after the Millennium so it would be all death being destroyed which is in Rev 20:14
It would be the last enemy left as satan and his angels and the unsaved would all be on the LOF so the last enemy would be death itself. It no longer exists in Rev 21:
Rev 21:4 And God shall wipe away all tears from their eyes; and there shall be no more death, neither sorrow, nor crying, neither shall there be any more pain: for the former things are passed away.