Ya'akov's final charge to his children concludes, "V'zos asher dibeir lahem avihem vayivarch osam..." (49:28) This is the blessings that he gave them.
Blessings? Reuvain was told that he is impetuous. Shimon and Levi were told that they were guilty of murder, that they angered too quickly and plotted to do wrong. What kind of blessings are these? Ibn Ezra (48:1) writes in fact that what Ya'akov told his children was not a bracha -- it was a nevuah of their future. Afterwards, "vayivarech osam..." he gave them some blessing that is not recorded, but what was said until that point was prophecy (see also Ohr haChaim 49:28).
Ralbag disagrees and says that yes, even what was said to Reuvain, Shimon, and Levi is a bracha. It's a bracha to know you are impetuous. It's a bracha to know you anger easily. It's a bracha to know you are aggressive. When a person recognizes their own personality traits -- and I deliberately say traits and not flaws -- then they can control and channel those traits properly. It doesn't have to be a flaw if you are aware of it and manage it properly. The bracha Ya'akov gave his children is the bracha of self-awareness.