The Pilgrimage - 22:71
They serve besides Allah such and such, who have not been given any power, nor do they have any knowledge about them. These wrongdoers have no helper.
Those who take gods besides Allah, their deeds will be canceled and they will deserve Hell, and therefore they are wrongdoers to their own souls:
The Companies/39:65
It has been revealed to you and those before you that if you associate partners, all that you do will be in vain and you will be of the losers.
The Repentance/9:17
The idolaters should not frequent the mosques of Allah, while they are witnesses of their own disbelief. Their deeds have come to naught. They will abide in the Fire forever.
The Cattle/6:82
Those who believe and do not mix their faith with wrongdoing, they deserve security and they have found the truth.
Luqman/31:13
"When Lokman advised his son, he said: "My dear son, do not associate partners with Allah; surely shirk (associating partners with God) is a great wrong."