1: ἀπειλέω
(Strong's #546 — Verb — apeileo — ap-i-leh'-o )

is used of Christ, negatively, in 1—Peter 2:23; in the Middle Voice, Acts 4:17 , where some texts have the noun apeile in addition, hence the AV, "let us straitly threaten," lit., "let us threaten ... with threatening" (see THREATENING). (See also STRAITLY. )

2: προσαπειλέω
(Strong's #4324 — Verb — prosapeileo — pros-ap-i-leh'-o )

"to threaten further" (pros, and No. 1), occurs in the Middle Voice in Acts 4:21 .