First vs Second Death

Used four times in Scripture: Rev. 2:11, 20:6, 20:14; 21:8.
Death in strongs G2288 1) the death of the body
a) that separation (whether natural or violent) of the soul and the body by which the life on earth is ended
b) with the implied idea of future misery in hell
1) the power of death
c) since the nether world, the abode of the dead, was conceived as being very dark, it is equivalent to the region of thickest darkness i.e. figuratively, a region enveloped in the darkness of ignorance and sin
2) metaph., the loss of that life which alone is worthy of the name,
a) the misery of the soul arising from sin, which begins on earth but lasts and increases after the death of the body in hell
3) the miserable state of the wicked dead in hell
4) in the widest sense, death comprising all the miseries arising from sin, as well physical death as the loss of a life consecrated to G-d and blessed in him on earth, to be followed by wretchedness in hell.
G1208 1) the second, the other of two
The phrase is Jewish, and is opposed to the first death, or the death of the body; which is the effect of sin, and is appointed of G-d, and which the people of G-d die as well as others; but the second death is peculiar to wicked men.
That is, an eternal separation from G-d and the glory of his power; as what we commonly mean by final perdition. This is another rabbinical mode of speech in very frequent use, and by it they understand the punishment of hell in a future life.
The particular promise here is made to him that should "overcome;" that is, that would gain the victory in the persecutions which were to come upon them. The reference is to him who would show the sustaining power of religion in times of persecution; who would not yield his principles when opposed and persecuted; who would be triumphant when so many efforts were made to induce him to apostatize and abandon the cause.
Shall not be hurt of the second death. By a second death. That is, he will have nothing to fear in the future world. The punishment of hell is often called death, not in the sense that the soul will cease to exist, but
(a) Because death is the most fearful thing of which we have any knowledge, and
(b) Because there is a striking similarity, in many respects, between death and future punishment. Death cuts off from life--and so the second death cuts off from eternal life; death puts an end to all our hopes here, and the second death to all our hopes for ever; death is attended with terrors and alarms--the faint and feeble emblem of the terrors and alarms in the world of woe. The phrase, "the second death," is three times used elsewhere by John in this book, (Revelation 20:6, 14; 21:8) but does not occur elsewhere in the New Testament. The words death and to die, however, are not unfrequently used to denote the future punishment of the wicked.
The promise here made would be all that was necessary to sustain them in their trials.
"Affliction, like it, is bitter for the time being, but salutary; preserving the elect from corruption, and seasoning them for immortality, and gives scope for the exercise of the fragrantly breathing Christian virtues" [VITRINGA].
Nothing more is requisite to make the burdens of life tolerable than an assurance that, when we reach the end of our earthly journey, we have arrived at the close of suffering, and that beyond the grave there is no power that can harm us. Religion, indeed, does not promise to its friend’s exemption from death in one form. To none of the race has such a promise ever been made, and to but two has the favor been granted to pass to heaven without tasting death. It could have been granted to all the redeemed, but there were good reasons why it should not be; that is, why it would be better that even they who are to dwell in heaven should return to the dust, and sleep in the tomb, than that they should be removed by perpetual miracle, translating them to heaven. Religion, therefore, does not come to us with any promise that we shall not die. But it comes with the assurance that we shall be sustained in the dying hour; that the Redeemer will accompany us through the dark valley; that death to us will be a calm and quiet slumber, in the hope of awaking in the morning of the resurrection; that we shall be raised up again with bodies incorruptible and undecaying; and that beyond the grave we shall never fear death in any form. What more is needful to enable us to bear with patience the trials of this life, and to look upon death when it does come, disarmed as it is of its sting, (1 Corinthians 15:55-57) with calmness and peace?