What were some of Solomons failures?

Answer 1

Perhaps his worst mistake was marrying idol worshiping wives and concubines. These turned him away from the true God, and made things difficult for his kingdom, thereby effectively ending the golden age of Israel, and the most peaceful time of their history.

(1 Kings 11:1-6) .And King Sol′o·mon himself loved many foreign wives along with the daughter of Phar′aoh, Mo′ab·ite, Am′mon·ite, E′dom·ite, Si·do′ni·an [and] Hit′tite women, 2 from the nations of whom Jehovah had said to the sons of Israel: "YOU must not go in among them, and they themselves should not come in among YOU; truly they will incline YOUR heart to follow their gods." It was to them that Sol′o·mon clung to love [them]. 3 And he came to have seven hundred wives, princesses, and three hundred concubines; and his wives gradually inclined his heart. 4 And it came about in the time of Sol′o·mon's growing old that his wives themselves had inclined his heart to follow other gods; and his heart did not prove to be complete with Jehovah his God like the heart of David his father. 5 And Sol′o·mon began going after Ash′to·reth the goddess of the Si·do′ni·ans and after Mil′com the disgusting thing of the Am′mon·ites. 6 And Sol′o·mon began to do what was bad in the eyes of Jehovah, and he did not follow Jehovah fully like David his father.