K2Cr2O7 AND KMnO4 are oxidising agents.
The difference between them as folows:
KMnO4 is slightly stronger oxidising agent than K2Cr2O7 in acidic medium, however, KMnO4 can act as an oxidising agent in all the three medium(acidic/basic/neutral) and it acts a slightly weaker oxidising agent than K2Cr2O7 in basic or neutral medium.