Luke 2:43τελειωσάντων
When those days were over and they were returning home, the boy Jesus remained behind in Jerusalem, but His parents were unaware He had stayed.
John 17:23τετελειωμένοι
I in them and You in Me—that they may be perfectly united, so that the world may know that You sent Me and have loved them just as You have loved Me.
Acts 20:24τελειῶσαι
But I consider my life of no value to me, if only I may finish my course and complete the ministry I have received from the Lord Jesus—the ministry of testifying to the good news of God’s grace.
Philippians 3:12τετελείωμαι
Not that I have already obtained all this, or have already been made perfect, but I press on to take hold of that for which Christ Jesus took hold of me.
Hebrews 2:10τελειῶσαι
In bringing many sons to glory, it was fitting for God, for whom and through whom all things exist, to make the author of their salvation perfect through suffering.
1 John 2:5τετελείωται
But if anyone keeps His word, the love of God has been truly perfected in him. By this we know that we are in Him:

Abbott-Smith

τελειόω, -ῶ
(τέλειος), [in LXX: Exo.29:9, Lev.4:5, al. (τ. χεῖρ מָלֵא pi.), 2Ki.22:26, al. (תָּמַם), Wis.4:13, al. (cf. Westc., He., 64) ;]

1. bring to an end, finish, accomplish, fulfil: Jhn.4:34, Act.20:24; of time, Luk.2:43, Jhn.5:36 17:4; pass., ἡ γραφή, Jhn.19:28.

2. to bring to maturity or completeness, to complete, perfect;

(b) of persons, in ethical and spiritual sense: Heb.2:10 9:9 10:1, 14; pass., Luk.13:32, Jhn.17:23, Php.3:12, Heb.5:9 7:28 11:40 12:23, 1Jn.4:18 (for a different view of the meaning in Heb.2:10, al., see Rendall, in l).†
(AS)

Sources: Abbott-Smith’s Manual Greek Lexicon of the New Testament (1922, public domain) and glosses from STEPBible TBESG (CC BY 4.0); STEPBible TAGNT (Greek New Testament, CC BY 4.0); the Berean Standard Bible (public domain). Reformatted by Word Study, wording unchanged. All sources and licenses.