καὶ αὐτός ἐστιν ἡ κεφαλὴ τοῦ σώματος τῆς ἐκκλησίας·
ὅς ἐστιν ἀρχή,
πρωτότοκος ἐκ τῶν νεκρῶν,
ἵνα γένηται ἐν πᾶσιν αὐτὸς πρωτεύων
The reading above is from NA28.
ἡ κεφαλὴ-some want to understand this noun phrase as meaning "the source," but an article by Vern Poythress knocks down the argument. The phrase quite probably refers to one who has authority over another: Christ is the head of his ecclesia (ἡ κεφαλὴ τοῦ σώματος τῆς ἐκκλησίας). See 1 Corinthians 11:3.
Although ἀρχή is anarthrous, it is likely definite ("the beginning").
NET Bible: "He is the head of the body, the church, as well as the beginning . . . "
πρωτότοκος ἐκ τῶν νεκρῶν is a partitive genitive.
ἵνα γένηται ἐν πᾶσιν αὐτὸς πρωτεύων: "that in everything he might be preeminent" (ESV).
But compare YLT: "And himself is the head of the body -- the assembly -- who is a beginning, a first-born out of the dead, that he might become in all things -- himself -- first"
Young places the stress on Christ 'becoming' preeminent in all things and renders ἀρχή, "a beginning." But many commentators would agree with Richard R. Melick (Philippians, Colossians, Philemon), who insists that the verse should be translated: "He is the beginning, that is, the firstborn out of the dead."
While I part ways with John Eadie theologically, I still continue to admire his grammatical/exegetical skill:
Two distinct meanings have been assigned to ἐν πᾶσιν. 1. It may be taken as masculine, “among all persons,” as is the opinion of Anselm, Beza, Cocceius, Heinrichs, Piscator, and Usteri. If the clause referred simply to the νεκροί, of which Jesus is the first-born, then we should have expected the article- ἐν τοῖς πᾶσιν. That ἐν following πρωτεύω may refer to persons, Kypke has shown in his note on this verse, though παρά is the preposition as frequently employed, and more usually the simple genitive. 2. The phrase ἐν πᾶσιν is more naturally taken by the majority in a neuter sense, “in every thing,” or “in all respects.” This is the ordinary meaning of the phrase in the New Testament. 2 Corinthians 11:6; Ephesians 1:23; 1 Timothy 3:11; 2 Timothy 2:7; Titus 2:9; 1 Peter 4:11. The usus loquendi is therefore in favour of this interpretation, “first in all points;” or as Theophylact says, in all things- τοῖς περὶ αὐτὸν θεωρουμένοις—“in all things which have reference to Himself;” as Chrysostom has it, πανταχοῦ πρῶτος. The verb γένηται is not to be confounded with the verb of simple existence. The meaning is not that He might be, but that “He might become.”
Finally, NWT (2013) handles Colossians 1:18 thus: "and he is the head of the body, the congregation. He is the beginning, the firstborn from the dead, so that he might become the one who is first in all things"