Matthew 10:28 seems to do service for both the traditional and conditional views of the soul.
KJV Matthew 10:28 And fear not them which kill the body, but are not able to kill the soul: but rather fear him which is able to destroy both soul and body in hell.
TBT Matthew 10:28 καὶ μὴ φοβηθῆτε ἀπὸ τῶν ἀποκτεινόντων τὸ σῶμα, τὴν δὲ ψυχὴν μὴ δυναμένων ἀποκτεῖναι· φοβήθητε δὲ μᾶλλον τὸν δυνάμενον καὶ ψυχὴν καὶ σῶμα ἀπολέσαι ἐν γεέννῃ.
The Lord says do not be fearful of those who can kill the body but are not able to kill the soul rather fear him that is able to destroy both soul and body in gehenna (the valley south of Jerusalem where Moloch took live children sacrifices). which is used here of the second death.