The correct translation is indeed
Personne n'est arrivé
And as you correctly deducted, "personne" already has a negative meaning so you shouldn't combine it with "pas" (but keeping the
ne or in this case
n'). If you do so, it's called a
double négation. Double negations are usually tricky and therefore used very rarely and most of the time to induct confusion.
As in mathematics, double negation turns out to be positive.
Personne n'est pas arrivé (Nobody hasn't arrived)
Tout le monde est arrivé (Everybody has arrived)
or, if you want to use a plural ("Tout le monde" having a singular meaning being seen as one whole group)
Toutes les personnes sont arrivées (All the people have arrived)
where you should be careful not to mix up
la personne/les personnes the noun , meaning "the people" and
personne the pronoun meaning "nobody".
The Google translation you mention is indeed completely wrong but would be understood if ever you express it that way.
When refering to things instead of people,
rien (nothing) should be used instead of
personne (nobody). The grammatical use would be almost the same, at least regarding negation :
Tu n'as rien compris
... no "pas" in this sentence,
rien conveying negative meaning.
Note that in this case
rien comes between auxialiary and verb. "Tu n'as compris rien" isn't correct. I couldn't give a technical explanation about why though... I think your confusion might come from the fact
rien is actually translated differently in English depending you're speaking positively or negatively. Actually as I think about it I guess it's more correct in English too to use "not ... anything" than just "nothing". I already heard sentences like "I didn't do nothing", but it's not how I was taught English...