Throwing out the NKJV because of a scruple with one passage is rather unfair.
Forgive me if I seem unfair. Although I did mention only one passage (2 Thess. 2:7), my main concern was the possibility of dispensationalist bias elsewhere in the translation, seeing that it is rather present here. I recognize also that, with this particular verse, the problem partly lies with the choice of the translation to capitalize pronouns referring to deity. That forced them to make a choice. With translations that do not do this, leaving the pronoun un-capitalized would have relieved the translators the responsibility of making a conscious choice since it could be taken either way in that case.
If we go looking for bias it is likely that we'll find it, especially if we know what we're looking for. That's not to say it isn't there.
For an example, see the prophecies against the nations at the end of Jeremiah. Several times (e.g. 48:47, 49:6,39) the NKJV has "bring back the captives." Other translations have "bring again the captivity of" (KJV), "bring back the captivity of" (ASV) or "restore the fortunes of" (ESV, NIV, NASB, HCSB, RSV, NRSV.) The NASB has "captivity" in a footnote. The NET has "reverse Moab's ill fortune" in Jer. 48:47.
Some (especially those looking for bias) may say that the NKJV rendering is possible but that it is maybe slanted toward a restorationist (i.e. Zionist) literalistic interpretation as opposed to interpreting that phrase as a reference to salvation, etc. (In those cases, captivity not only refers to Israel being returned to the land but Moab, Elam etc., not that that matters from a doctrinal perspective.)
I don't know Hebrew and don't even know of the NKJV here is really different than the KJV. (I think they are probably saying the same thing, especially the ASV and NKJV. And the NKJV tends to follow the KJV (as opposed to other modern translations) unless they really think it needs improvement.) But "bring back the captives" seems to me (a complete amateur to be sure) to point to more of a particular interpretation than "restore the fortunes of" does. The latter appears to be a more general term. On the other hand, the dispensationalist (or other "Christian Zionist") might allege that the other modern translations show the evidence of replacement theology/supersessionism here and that it started with the liberal RSV.
Regardless, if one only had the ESV and NKJV to compare, one could say "Aha!" and allege bias one way or the other.
I'll note a few more examples of alleged bias in modern translations. I can think of at least one passage in the ESV (Micah 5:2) in which some allege that a liberal (i.e. anti-supernatural) rendering from the RSV has been retained even though it is generally acknowledged that the ESV committee generally fixed the problems elsewhere. Other conservatives say it (Micah 5:2 in the ESV) is the correct rendering despite the controversy. Those looking for liberal bias in the ESV can find more examples, I'm sure, the validity of which will probably be debatable. Then there's the allegation of political correctness with their refusal to use "slave" instead of "bondservant" or whatever, with the video discussion by the ESV committee being used as evidence by those making the charge.
To give another example of how a translation is viewed by various camps, the NIV84 is alleged by various Arminians, Lutherans, and Semi-Pelagianistic Baptists to show evidence of a Calvinist bias in various passages. One anti-Calvinist blogger even blames the NIV for being a significant factor in the rise of the "New Calvinism" over the past 10-15 years as most of the leaders would have cut their teeth on it. I've seen some Lutherans say that it is ironic that so many Calvinists were quick to adopt the ESV because in their view the NIV is a more Calvinistic translation. Others say it has a premillennial and perhaps even a dispensational bias. But dispensationalists and other Christian Zionists strongly object to its rendering of Gal 6:16 since it rules out their interpretation.
If you are looking for a safe "Reformed" Bible, I think you'll have to opt for the Geneva or KJV. Every other one has had Baptists, dispensationalists, Arminians, liberals (RSV, forerunner of the ESV, which is only a light revision of it) and allegedly even a Unitarian(s) (ASV, forerunner of the RSV and NASB) on the translation committee, maybe among others. At least one person involved in the NIV was homosexual. I'm sure we can dig into the personal lives of the KJV translators (or James I himself) and make
ad hominem attacks as well, whether legitimate or not.
It was either a post by someone here or the review of the NKJV by the Trinitarian Bible Society that gave several examples of the NKJV being less "Calvinistic" than the AV in certain passages.
I have to confess that I've spent way too much time over the past 15+ years trying to figure out which Bible to use instead of just reading one.