The Targums place Nimrod very blatantly "in defiance of the Lord." Adam Clarke makes mention of them in his commentary for verse 8:
Nimrod - Of this person little is known, as he is not mentioned except here and in 1 Chronicles 1:10, which is evidently a copy of the text in Genesis. He is called a mighty hunter before the Lord; and from Genesis 10:10, we learn that he founded a kingdom which included the cities Babel, Erech, Accad, and Calneh, in the land of Shinar. Though the words are not definite, it is very likely he was a very bad man. His name Nimrod comes from מרד, marad, he rebelled; and the Targum, on 1 Chronicles 1:10, says: Nimrod began to be a mighty man in sin, a murderer of innocent men, and a rebel before the Lord. The Jerusalem Targum says: "He was mighty in hunting (or in prey) and in sin before God, for he was a hunter of the children of men in their languages; and he said unto them, Depart from the religion of Shem, and cleave to the institutes of Nimrod." The Targum of Jonathan ben Uzziel says: "From the foundation of the world none was ever found like Nimrod, powerful in hunting, and in rebellions against the Lord." The Syriac calls him a warlike giant. The word ציד tsayid, which we render hunter, signifies prey; and is applied in the Scriptures to the hunting of men by persecution, oppression, and tyranny. Hence it is likely that Nimrod, having acquired power, used it in tyranny and oppression; and by rapine and violence founded that domination which was the first distinguished by the name of a kingdom on the face of the earth. How many kingdoms have been founded in the same way, in various ages and nations from that time to the present! From the Nimrods of the earth, God deliver the world!
John Gill has a fascinating write-up in his commentary for verse 8 that equates Nimrod with Bacchus, and that Nimrod was the first to form an official government:
And Cush begat Nimrod
Besides the other five sons before mentioned; and probably this was his youngest son, being mentioned last; or however he is reserved to this place, because more was to be spoken of him than of any of the rest. Sir Walter RaleighF9 thinks that Nimrod was begotten by Cush after his other children were become fathers, and of a later time than some of his grandchildren and nephews: and indeed the sons of Raamah, the fourth son of Cush, are taken notice of before him: however, the Arabic writersF11 must be wrong, who make him to be the son of Canaan, whereas it is so clear and express from hence that he was the son of Cush. In the Greek version he is called Nebrod, and by Josephus, Nebrodes, which is a name of Bacchus; and indeed Nimrod is the same with the Bacchus of the Heathens, for Bacchus is no other than Barchus, the son of Cush; and Jacchus, which is another of his names in Jah of Cush, or the god the son of Cush; and it is with respect to his original name Nebrod, or Nebrodes, that Bacchus is represented as clothed with the skin of νεβρις, "nebris", or a young hind, as were also his priests; and so in his name Nimrod there may be an allusion to נמרא, "Nimra", which, in the Chaldee language, signifies a tiger, and which kind of creatures, with others, he might hunt; tigers drew in the chariot of Bacchus, and he was sometimes clothed with the skin of one; though the name of Nimrod is usually derived from מרד, "to rebel", because he was a rebel against God, as is generally said; and because, as Jarchi observes, he caused all the world to rebel against God, by the advice he gave to the generation of the division, or confusion of languages, the builders of Babel: he seems to be the same with Belus, the founder of Babel and of the Babylonian empire, whom Diodorus SiculusF12 confounds with Ninus his son:
he began to be a mighty man in the earth:
that is, he was the first that formed a plan of government, and brought men into subjection to it; and so the JewsF13 make him to be the first king after God; for of the ten kings they speak of in the world, God is the first, and Nimrod the second; and so the Arabic writersF14 say, he was the first of the kings that were in the land of Babylon; and that, seeing the figure of a crown in the heaven, he got a golden one made like it, and put it on his head; hence it was commonly reported, that the crown descended to him from heaven; for this refers not to his gigantic stature, as if he was a giant, as the Septuagint render it; or a strong robust man, as Onkelos; nor to his moral character, as the Targum of Jonathan, which is,
"he began to be mighty in sin, and to rebel before the Lord in the earth;"
but to his civil character, as a ruler and governor: he was the first that reduced bodies of people and various cities into one form of government, and became the head of them; either by force and usurpation, or it may be with the consent of the people, through his persuasion of them, and on account of the mighty and heroic actions done by him.
F9 History of the World, B. 1. ch. 10. sect. 1. p. 109.
F11 Elmacinus, p. 29. apud Hottinger. Smegma, p. 270. See the Universal History, vol. 1. p. 276.
F12 Bibliothec. l. 2. p. 90.
F13 Pirke Eliezer, c. 11.
F14 Elmacinus, p. 29. Patricides, p. 16. apud Hottinger. Smegma, p. 271, 272. Abulpharag. Hist. Dynast. p. 18.
John Gill continues in his commentary for verse 9 to surmise that Nimrod perhaps got his start with hunting animals that annoyed certain settlements, which he might have used to gain a following and influence over the inhabitants of the land. Gill also quotes the Targums and Septuagint for the idea that Nimrod was in opposition to the Lord:
He was a mighty hunter before the Lord
Which might be literally true; for, from the time of the flood to his days, wild beasts might increase very much, and greatly annoy men who dwelt very likely for the most part in tents scattered up and down in divers places: so that he did a good office in hunting and destroying them. An Arabic writerF15, of some authority in the eastern parts, says, that by hunting he got food sufficient for the builders of Babel, while they were employed therein; and Aben Ezra interprets it in his favour, that he built altars, and the creatures he took in hunting he offered them on them a burnt offering to God. But neither of these is probable; however, it may be observed, that in this way by hunting he arrived to the power and dominion over men he afterwards had; for not only he ingratiated himself into their favour by hunting down and destroying the wild beasts which molested them, but by these means he might gather together a large number of young men, strong and robust, to join him in hunting; whereby they were inured to hardships, and trained up to military exercises, and were taught the way of destroying men as well as beasts; and by whose help and assistance he might arrive to the government he had over men; and hunting, according to AristotleF16, is a part of the military art, which is to be used both on beasts, and on such men who are made to be ruled, but are not willing; and it appears, from XenophonF17, that the kings of Persia were fitted for war and government by hunting, and which is still reckoned in many countries a part of royal education. And it may be remarked, that, as Nimrod and Bacchus are the same, as before observed, one of the titles of Bacchus is ζαγρευς, "an hunter". CedrenusF18 says, that the Assyrians deified Nebrod, or Nimrod, and placed him among the constellations of heaven, and called him Orion; the same first discovered the art of hunting, therefore they joined to Orion the star called the dog star. However, besides his being in a literal sense an hunter, he was in a figurative sense one, a tyrannical ruler and governor of men. The Targum of Jonathan is;
"he was a powerful rebel before the Lord;"
and that of Jerusalem,
"he was powerful in hunting in sin before the Lord,"
and another Jewish writerF19 says, he was called a mighty hunter, because he was all his days taking provinces by force, and spoiling others of their substance; and that he was "before the Lord", truly so, and he seeing and taking notice of it, openly and publicly, and without fear of him, and in a bold and impudent manner, in despite of him, see Genesis 6:11; 13:13. The Septuagint render it, "against the Lord"; he intended, as Jarchi's note is, to provoke him to his face:
wherefore it is said;
in a proverbial way, when any man is grown mighty and powerful, or is notoriously wicked, or is become a tyrant and an oppressor of the people, that he is
even as Nimrod the mighty hunter before the Lord.
This was a proverb used in the times of Moses, as it is common now with us to call a hunter Nimrod.
F15 Abulpharag. Hist. Dynast. p. 18.
F16 Politic. l. 1. c. 8.
F17 Cyropaed. l. 1. c. 5.
F18 Apud Abrami Pharum, l. 5. sect. 6. p. 128.
F19 R. Gedaliah, Shalshalet Hakabala, fol. 76. 2.
Nimrod was definitely a very capable man; for though he was a hunter, Genesis 10:10-11 conveys that he had a kingdom, which included cities such as Babel and Nineveh. Skill and prowess in hunting were often considered good qualities for proving yourself, with even David using this to convince King Saul to let him fight Goliath:
33 And Saul said to David, “You are not able to go against this Philistine [Goliath] to fight with him; for you are a youth, and he a man of war from his youth.”
34 But David said to Saul, “Your servant used to keep his father’s sheep, and when a lion or a bear came and took a lamb out of the flock, 35 I went out after it and struck it, and delivered the lamb from its mouth; and when it arose against me, I caught it by its beard, and struck and killed it. 36 Your servant has killed both lion and bear; and this uncircumcised Philistine will be like one of them, seeing he has defied the armies of the living God.” 37 Moreover David said, “The Lord, who delivered me from the paw of the lion and from the paw of the bear, He will deliver me from the hand of this Philistine.”
And Saul said to David, “Go, and the Lord be with you!” 1 Samuel 17:33-37 (NKJV)
While David was not actively hunting the lion and the bear and only killed them in defense of his sheep, his victories over these animals proved his worth to the king to allow him to do battle with men.
In the same way, Nimrod perhaps used his prowess with hunting animals to win over the confidence of the people of his day, eventually allowing him to become the ruler of his own kingdom. Babel is the same as Babylon, and Babylon is most often portrayed in Scripture as being opposed to the true God and His people. So it is not too much of a conjecture (and a conjecture it certainly is) to imagine that Nimrod's life might have been lived in opposition to the Lord, or in defiance of the Lord.