Tradition
2 Peter 3:15-16
As also our most dear brother Paul... hath written to you: As also in all his epistles... in which are certain things hard to be understood, which the unlearned and unstable wrest, as they do also the other scriptures, to their own destruction.
Context of the passage
Peter, near the end of his life, comments on Paul's letters and warns that Scripture is being misinterpreted by unstable teachers.
Catholic reading
Peter's warning that even Paul's letters are 'hard to understand' and easily 'wrested' by the untaught demonstrates that Scripture alone, without an authoritative interpreter, leads to error, an argument against sola scriptura from within Scripture itself.
Common objection
Peter is only warning about false teachers twisting Scripture, not denying that ordinary believers can read Scripture rightly with the Spirit's help.
Response
Even accepting that reading, Peter's remedy is not 'read more carefully alone' but implicitly points to the apostolic community's guidance, since he himself, an apostle with unique authority, is writing to correct the confusion, not merely urging private study.