Is Haddith Written 120 Years After the Prophet?

The Quran describes the prophet as a mercy unto mankind or to the universe. And then you come across claims of Haddith where the prophet was allegedly violent. The early Muslims of the Muayataz-Lad tradition and others also had deep reservations about Haddith. My issue really is that we've lost that critical approach among today's Muslims when it comes to Haddith literature, because it was written at least 120 years after the prophet.