Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
pardon [ˈpɑːdn] n (LAW) поми́лование
vt проща́ть (прости́ть*perf) (LAW) поми́ловать (perf)
pardon me!, I beg your pardon! прошу́ проще́ния!
(I beg your) pardon?, (US) pardon me? (what did you say?) прости́те, не расслы́шал
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.