Here in Part 3 we see the last part of the song. Both guitars play the same riffs here, except that at the very end Hanneman starts using higher octave chords. Don't forget the song is in Eb tuning, which means tuning each string down by 1 fret:

Low Eb : Ab : Db : Gb : Bb : Eb*

* although we're in Eb tuning, we'll use standard tuning chord names as most people will be more familiar with them.

At this point of the song the tempo increases again. It becomes as fast as Part 1, which means returning to thrash riffs using lots of drilling (fast palm-muted alternate picking), particularly on the Low E string. The last part of the song involves repeating the main chorus / verse riffs we saw in Part 1.

Solo Backing - We're not including the solos here (Slayer solos are nuts and involve too much weird whammy bar stuff). But here we still see the main backing riffs used at this point of the song. The riff here is similar to the stuff we saw in part 1:

Low E5 - drill - Bb5 - drill - F#5 - drill - Bb5 - drill - end lick - Repeat this 3 more times.

Next the song plays the same short riff encountered in part 1. This is:

Repetitive Riff - Same as Part 1, end on the F#5 and repeat 3 more times. Later the same riff shifts up to Fret 4, ending on D5 (repeat).

After plenty of that, it's back to the Chorus:

Chorus - The song ends on the chorus riff again. It's the same riff we saw in Part 1, except that towards the end Hanneman plays higher powerchords to build the ending, starting with this E5 (octave chord).