Οὗτος μὲν οὖν ἐκτήσατο χωρίον ἐκ μισθοῦ τῆς ἀδικίας, καὶ πρηνὴς γενόμενος ἐλάκησεν μέσος, καὶ ἐξεχύθη πάντα τὰ σπλάγχνα αὐτοῦ.
Now this man acquired a field with the reward of his unjust deed, and falling headfirst he burst open in the middle and all his intestines gushed out.
This is a vivid and rather horrifying description of Judas's end; it is the subject of much discussion, which the reader can find at the biblehub.com site, under 'Commentary' for Acts 1:18.
That οὗτος refers to Judas must be inferred from the context of previous verses.Οὗτος is the 'near' demonstrative pronoun, meaning something like 'this, the person/thing that we were just talking about'. The 'far' demonstrative pronoun (ἐκεῖνος, η, ο) is more like 'that', 'the person/thing over there or further away'.
There are four actions in this verse:
1 Judas acquired or possessed a field: ἐκτήσατο
Ἐκτήσατο is parsed as the 3-S (subject: Judas) aorist middle indicative of κτάομαι ('I acquire, purchase, possess'). I would consider κτάομαι a deponent verb, in that it has no active forms; the meaning makes sense as a middle - 'I do something (for myself)'.
The neuter noun χωρίον, 'field, piece of land', is the direct object of ἐκτήσατο.
2 Judas fell headlong: πρηνὴς γενόμενος
3 Judas burst open in the middle: ἐλάκησεν μέσος
Γενόμενος is not an indicative verb form; it is the masculine singular nominative form (referring again to Judas) of the aorist participle of γίνομαι.
Πρηνής is found only here in the NT; a hapax legomenon. It means something like 'headfirst' or 'headlong'. It has been suggested that the English 'prone' is etymologically related, but that seems to be questionable.
Ἐλάκησεν is another hapax legomenon; the 3-S (Judas again), aorist active indicative, of λάσκω.
Here we have a question. Λάσκω is used by classical authors, from Homer down. It has various uses, including:
There is apparently no classical use suggesting a body breaking open, nor - as best I can tell - is the verb found in the Septuagint.
Commentaries have suggested a variety of things, including that Judas's body burst open 'with a loud sound', which seems odd at best. I suggest 'he screamed from deep within' as a possible alternative.
4 His internal organs spilled out: ἐξεχύθη πάντα τὰ σπλάγχνα αὐτοῦ
Here the subject is not Judas, but his internal organs (τὰ σπλάγχνα αὐτοῦ). Ἐξεχύθη is parsed as 3-S, aorist active indicative, ἐκχέω - 'I pour out'. I believe that ἐξεχύθη is singular rather than plural because of τα ζώα τρέχει, where neuter plurals can use a singular verb.