Whatever his father had been, he was dead now, and this boy was on a path bent for destruction. He was unhappy with his situation in life, his family, his parentage, and with authority in general. So, with the help of his uncles and grandfather, and some hooligans off the streets, he murdered 70 of the children of his father. That left only himself to take over as King. This was the act that caused a curse to fall on Abimelech, the son of a "Mistress" to his father Gideon, the heroic judge of the Old Testament Bible.
When Gideon died, Abimelech disliked the fact that he would have no real rights to inheritance of his father's wealth and power. Abimelech had 70 half brothers, and he raised a band of thugs to help slaughter them all at once. All that is but one. The youngest son, Jotham, escaped. When Jotham heard the news that his brother was made king, he came to the edge of town on a high hill and shouted out a curse, in the form of a riddle or parable. He spoke a curse that God would cause Abimelech and his mother's family, who had helped put him into power, would turn on each other, and destroy each other in the end. Then, Jotham ran and remained in hiding as a political refugee.
For three years, Abimelech reigned in peace, though he was an evil man. Then, it happened that "bad blood" rose up between him and his wicked kinfolks. They say what goes around, comes around. Likewise it did with these murderous men who had helped him with the rampage against his brothers. They began to hate Abimelech. Then a loud mouth trouble-maker came into town, talking loud, and bragging about what he would do to this Abimelech if he got his hands on him. He suggested that he would make a better king himself and offered to raise an army against him. He did, but was routed brutally, then Abimelech came after his uncles who had sent the man after him. He trapped them in a tower and set fire to it, killing them all. Heading to the next tower, where more were hiding, he laid siege to it as well, but a woman threw a heavy rock down on his head. He didn't want it to be said that he was killed by a woman, so he asked one of his men to kill him, so the man drew his sword and ended the life of a son who had killed so many of the children of his father and grandfather.
Judges 6:12-13 And the angel of the LORD appeared unto him, and said unto him, The LORD is with you, you mighty man of valor. And Gideon said unto him, Oh my Lord, if the LORD be with us, why then is all this befallen us? and where are all his miracles which our fathers told us of... but now the LORD has forsaken us...
Judges 9:56, Micah 2:1, Matthew 18:7