Is it a sin to make Dua for hardship or a calamity to come down on a regular person, or to damn them with a La'na, for an injustice they have caused you?
Real Muslim prays for the good for every one. We should pray for those wronged us and did injustice on us to be guided to the truth and to leave wrong way to the right way.
'We don't curse any believer. We only curse the enemies of Allah (SWT), the Prophet (SAWA) and Ahlul Bayt (AS) who are in fact the enemies of mankind.
'Wassalam.