Exegesis:
hupodeixō de humin tina phobēthēte ‘I will show you whom you have to fear.’ For hupodeiknumi cf. on 3.7. phobēthēte is aorist subjunctive, here used in a subordinate clause, see below.
phobēthēte ton … echonta … ‘fear him who has….’ Here phobēthēte is aorist imperative, used in a main clause. It is followed by an accusative and this may suggest that here a different type of fearing is implied, i.e. the fear of God, to whom ton … echonta is best understood to refer.
meta to apokteinai ‘after killing,’ takes up meta tauta in v. 4.
exousian embalein eis tēn geennan ‘power to throw into hell,’ dependent upon echonta. The phrase refers to the power to condemn, not the power to destroy. For exousia cf. on 4.32.
emballō ‘to throw into,’ with eis following.
geenna ‘hell,’ place of eschatological punishment.
nai, legō humin ‘yes, or, indeed, I tell you,’ cf. on 3.8. nai is added in order to stress that the subsequent statement serves to affirm emphatically the preceding one.
Translation:
Warn, or, ‘make clear/explain’ (Toraja-Sa’dan), or simply, ‘tell.’
Whom to fear, or, “the only One you need to fear” (Phillips), ‘who (it is) that you really should fear’ (Balinese). For fear with reference to God see 1.50.
Who, after he has killed, has power to cast, or, ‘who has power (first) to kill and then to cast,’ ‘who not only kills, but also has power to cast.’ Kills, or, ‘causes to die’; in Balinese God cannot be said ‘to kill a person,’ but ‘to take-away a person’s life.’ The verb may require an object, e.g. ‘you,’ ‘a man’ (Balinese), ‘your-body’ (Tae’ 1933). Cast, or, ‘hurl down,’ ‘send,’ ‘cause to descend/fall/go.’ Since the persons in question are envisaged now as dead, an object, if required, may have to be a specific term used to refer to dead persons, cf. e.g. Tae’ 1933.
Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.