Definition of "hainous"

But be the fact never so hainous (Murther it self) they can put none to death.

1681, Robert Knox, An Historical Relation Of The Island Ceylon In The East Indies‎

For the Minister of Justice who have hitherto lived in India, through their obscure and damnable blindness, were not much sollicitous about the punishment of the Crimes and Butcheries which have been and are still committed by these Tyrants, only they may say possibly because such a one, and such a one hath wickedly and barbarously dealt with the Indians, that is the reason so great a summ of Crowns in Money is diminished already or retrenched from His Majesties Annual Revenue, and this general and confused proof is sufficient (as they worthily conceive) to purge or repress such great and hainous Crimes.

1689, Bartolome de las Casas, A Brief Account of the Destruction of the Indies‎

But he having in one year's time filled that place with principles of rigid separation, and tending to Anabaptistry, the prudent Magistrates of the Massachusetts Jurisdiction, sent to the Church of Salem, desiring them to forbear calling him to office, which they not hearkening to, was a cause of much disturbance; for Mr. Williams had begun, and then being in office, he proceeded more vigorously to vent many dangerous opinions, as amongst many others these were some; That it is not lawful for an unregenerate man to pray, nor to take an Oath, and in special, not the Oath of Fidelity to the Civil Government; nor was it lawful for a godly man to have communion either in Family Prayer, or in an Oath with such as they judged unregenerate: and therefore he himself refused the Oath of Fidelity, and taught others so to do; also, That it was not lawful so much as to hear the godly Ministers of England, when any occasionally went thither; & therefore he admonished any Church-members that had done so, as for hainous sin: also he spake dangerous words against the Patent, which was the foundation of the Government of the Massachusets Colony: also he affirmed, That the Magistrates had nothing to do in matters of the first Table [of the commandments], but only the second; and that there should be a general and unlimited Toleration of all Religions, and for any man to be punished for any matters of his Conscience, was persecution....

1733, Various, Great Epochs in American History, Vol. II‎