Broly

Personality
rather calm and shy while under control by the control ring and rather unstable and sadistic and being under pure rage and no mind with no thought while not under this control he is shy but rather smart and manipulative using this intelligence to kill his father Baragus and lose control from his father due to act of his murder

History
being rather a bad case since birth as having a power higher than the king who warned Baragus of this unstable Nature due to this great power since birth and plans a killing of the boy and murders them with ki blast who broly as a baby effortlessly blocks this attack and saves him and his father who later on who accept the fact that vegeta was right and at that point having no option and after years of uncontrollable power Baragus puts a device to stabilize his mental state which years later would backfire as the divide between broly's power and limits on the device started to make it malfunction until kakarot or son goku showed up at his planet eager to test his power and getting defeated and then later on he had to get his revenge on goku for his death and having a zenkai made him even more powerful and his lose sense of self at this point due to the brain damage and great pain received on his scar wound and the amount of damage he took from planet's explosion after and with all this in mind he came for revenge with last bit of sanity he had with him gaining his mind back mere moment to recognize his father meant well and to to the afterlife in peace and with this ends the story of Broly

Power
being at the level of a super saiyan 3 goku in his final form as well as being stronger than king vegeta at birth and utterly being defenseless to stabbing as he was a baby he took zero damage from with the cocky king vegeta having a beam attack for them rebelling against him with broly as a baby effortless blocks it and flys off and effortless beating the crap out of all the z fighters and fighting Gohan Goten and trunks at once with no effort only losing these fights due to not having any fighting skill and just being a rage monster as Baragus quoted