Picture

The caption says that Theseus is not afraid but fights valiantly and kills the Minotaur. Ever heard of tauro machy (bull fighting, very popular in Spanish speaking countries:
ταύροις (dat.) μάχονται, they fight against bulls?

διὰ τί οὐ φοβεῖται ὁ Θησεύς;
ἀνδρεῖός ἐστιν. ἀνδρείως οὖν προσχωρεῖ τῷ Μινοταύρῳ.
ἰσχυρός ἐστιν, καὶ τὸ τῆς Ἀριάδνης ξίφος ἔχει. ἀνδρείως οὖν μάχεται . 
καὶ ὁ Μινώταυρος μάλα ἰσχυρός ἐστιν. ἀγρίως ὁρμᾶ ἐπὶ τὸν Θησέα.
πολὺν χρόνον μάχονται.
τέλος δὲ ὁ Θησεὺς τὸν Μινώταυρον τύπτει τῷ ξίφει καὶ ἀποκτείνει αὐτόν.
οἱ δὲ τοῦ  Θησέως ἑταῖροι μάλα θαυμάζουσι καὶ χαίρουσιν.
ὡς ἀνδρεῖός ἐστιν ὁ Θησεύς.

A little combination Theseus here and Philip in lesson 5b with his opponent Mr. Wolf.
We could δήπου (I suppose) have used other words from that lesson as well:

ἐμπίπτει τῷ Θησεῖ
δεινὸν ψόφον 
or θόρυβον ποιοῦσιν
ὁ Θησεύς οὐκ ἀναστρέφει
ὁ Μινώταυρος ἀσπαίρει
πίπτει, καταπίπτει πρὸς τὴν γῆν

Here we have: ἀποκτείνει present tense: he kills
in 5b it was:   ἀπκτονε   he has done it and there is a result: the beast is dead.