Are there any sins opposed to this virtue?
Yes, there are a number of sins which are opposed thereto either by excess or defect.
What are the sins opposed to magnanimity by excess?
They are presumption, ambition, and vainglory (CXXX.-CXXXII.).
How are these different sins distinguished from each other?
In this, that presumption inclines one to the performance of acts that are too much for one's capabilities; ambition seeks honours greater than one deserves; and vainglory seeks some glory that has either no object, or that has an object of little worth, or which is not directed to the one true end which is the honour of God and the welfare of men (ibid.).
Is vainglory a capital sin?
Yes, for it implies the showing off of one's own excellence which one seeks in everything, and which may lead one to commit all manner of sins (CXXXII. 4).
What are the daughters of vainglory?
They are boasting, hypocrisy, stubbornness, discord, strife, and disobedience (CXXXII. 5).
Next - The Catechism of the Summa - XLIII. OF THE VIRTUES ANNEXED TO FORTITUDE; OF MAGNANIMITY; OF THE SINS OPPOSED TO MAGNANIMITY; VIZ., OF PRESUMPTION; OF AMBITION; OF VAINGLORY; AND OF PUSILLANIMITY (C)