You guessed it. The answer is MEGADETH. Slayer Clinches the number 2 slot and Metallica slightly edges out Anthrax for 3 because it has more unique words.
Does this mean that lyrically Megadeth has the smartest lyrics, the best phrasing, rhyming, scansion?
No, its all a matter of taste, it just means they have the largest vocabulary of the big 4. Its a fun factoid.
Methodology:
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Largest number of words counting only one occurrence each:
Megadeth: 4,535
Slayer: 4,136
Anthrax: 3,431
Metallica: 2,964
Largest number of unique words- occurring only once in the entire catalog:
Megadeth: 2,259
Slayer: 1,937
Metallica: 1,235
Anthrax: 1,035
Darklyrics.com was used for all word counting
Metallica, Megadeth, Slayer, Anthrax
Lyrical Showdown:
Of the Big Four who has the largest lyrical vocabulary?