“They will say I was an underachiever.”

[Michael Zwingli]

Incuriosus gloriae may capture a good bit of one possible meaning of "underachiever," that is, not particularly interested in doing what one can to leverage one's strengths to attain reputation or fame.

Viam fēcistī!

 

[Pacifica]

I do think, though, that the "b" of sub- is assimilated before "p", which would make it supperventor.

It would always be assimilated in pronunciation, I believe (try actually pronouncing "bp"...), but not necessarily in spelling.

Sure, it is unclear whether the concept of "the underachiever" would have been recognized by a Roman of any social class. Certainly, certain types of behavior were expected from those born within the varying social classes of the Roman republic, as is clear demonstrated by Tacitus in his Annals: "...Mamercus Scaurus, insignis nobilitate et orandis causis, vita probrosus." (Annals Book VI, 29), but whether someone who had all the advantages of a noble birth, yet was not "...distinguished by his talent as an advocate" or in any other way would be viewed as an "underachiever" within Roman society, is quite uncertain. Even so, our Nicolaus is not writing for the Romans, who now speak Italian, but for himself and for others of us today, wherein we do have the idea of the "underachiever". Certainly, Latin is a "dead" language, but if Latin is to be useful to us, and used by us today, then it seems to me that we need not, of necessity, make reference to ancient Roman concepts when trying to express our own.

To what extent we should stick to Roman usage is a matter of debate, but that coinage is so strange that even most present-day Latinists probably wouldn't know what it was supposed to mean. Pervenio isn't such an obvious translation for "achieve", in the first place, nor is sub- usually suffixed to verbs and verbal nouns to mean "too little" like under- in English.

 

[Michael Zwingli]

...nor is sub- usually suffixed to verbs and verbal nouns to mean "too little" like under- in English

Yes, I was thinking of that initially, with sub- rendering a definite spatial/directional sense in Latin...

 

[Agrippa]

... if Latin is to be useful to us beyond helping us to think better, and is to be used by us today as we find it useful, then it seems to me that we need not, of necessity, make reference to ancient Roman concepts when trying to express our own. ...

Btw, there is a detailed discussion of this very problem:

Erasmi Roterodami dialogus cui titulus
Ciceronianus sive de Optimo dicendi genere.

Latin: https://books.google.de/books?id=YIdEAAAAcAAJ&printsec=frontcover&dq=erasmus+ciceronianus&hl=en&sa=X&redir_esc=y#v=onepage&q&f=false

English translation: https://archive.org/details/ciceronianusorad00erasuoft