What is your advice to a man who constantly curses his wife over the trivialest of reasons, even though all his marital rights are fulfilled?

It is not permissible for a husband to curse his wife, whether she is remiss or not, because cursing a believer is like killing him, and reviling is فسوق (disobedience/transgression). A believer is not one who slanders or curses. Those who curse will not be witnesses or intercessors on the Day of Resurrection. The husband must repent to Allah and seek forgiveness from his wife, treat her kindly, and be a good role model for her and their children.