Paul Barnett, The Second Epistle to the Corinthians (NICNT) -- Somewhat moderate evangelical. Helpful insights into the Greek and cultural context.
John Calvin, Second Corinthians -- Solid. Does a great job summarizing the overall argument of the letter.
John Gill, Second Corinthians -- Solid.
Charles Hodge, 1 and 2 Corinthians -- Interesting and helpful.
Colin G. Kruse, Second Corinthians (TNTC) -- Very helpful overview
Thomas Aquinas, Commentary on the Letters of Saint Paul to the Corinthians -- Really interesting and often insightful. Please note that portions of the commentary on 1 Corinthians are from Peter of Tarentaise (d. 1175). Published by The Aquinas Institute for the Study of Sacred Doctrine.