Annihilationism is the correct (scriptural) one. -
Sincerely Dead Dying, To Know Jesus by brother Aaron Earnest : Free Download, Borrow, and Streaming : Internet Archive
Job_21:30 That the wicked is reserved to the day of destruction? they shall be brought forth to the day of wrath.
Job_31:3 Is not destruction to the wicked? and a strange punishment to the workers of iniquity?
ETC - Eternal Conscious Torment is unjust, non-merciful, and ultimately places God in the position of sustaining sin.
Universalism - is unjust (no justice), and mercy would mean nothing.
As for your question, God is love (1 John 4:8,16 KJB), and in that love is justice / mercy together (Exo. 20:6-7; 34:6-7 KJB).
Joh 3:16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
Rom_6:23 For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord.
As it was in the great flood, so it will be in the great fire to come.
7 Bible Commentary, 935-936 - SDA Bible Commentary, vol. 7 (Ellen G. White), page 935
“...
[page 935] His
mercy was not weakness, but
a terrible power to punish sin because it is sin, yet a power to draw to it the love of humanity.” -
EGW SDA Bible Commentary, vol. 7
The Great Controversy (1911), by Ellen G. White, page 543
“...
[page 543] “In
mercy to the world,
God blotted out its wicked inhabitants in Noah’s time. In
mercy He
destroyed the corrupt dwellers in Sodom. Through the deceptive power of Satan the workers of iniquity obtain sympathy and admiration, and are thus constantly leading others to rebellion. It was so in Cain’s and Noah’s day, and in the time of Abraham and Lot; it is so in our time. It is
mercy to the universe that God will
finally destroy the rejecters of His grace.” -
The Great Controversy
The destruction (annihilation) of the finally impenitent (satan, all his followers) is loving, to them, and to the rest of the redeemed, and unfallen universe. It is also done in the justice & mercy of JEHOVAH Elohiym. The trial of sin and its results will have been fully witnessed by all, and the verdict will Amen God's character.