The phrase to give credit where credit is due, and its variants, mean to acknowledge merit or achievement when it is deserved, even if one is reluctant to do so.

This phrase occurs, for example, in Lettuce rejoice: inside story of Daily Star iceberg’s triumph over Liz Truss, by Jim Waterson, Media Editor, published in The Guardian (London and Manchester, England) of Friday 21^st October 2022:

Exactly who holds power in Britain right now? In terms of global attention from world leaders, news coverage, and a strong political record of success it may just be a decaying lettuce called Lizzy owned by the Daily Star.
The rapidly greying vegetable, which emerged triumphant from a showdown with Liz Truss over who would last longer, is at a domestic residence in an undisclosed location, according to the newspaper’s deputy editor Jon Livesey. […]
[…]
A reporter was dispatched to Tesco to spend 60p on an iceberg lettuce with an expected lifespan of up to 10 days. Bookmakers were phoned up to provide odds on whether the lettuce or Truss would last longer. As part of an effort to embrace a multimedia world, a decision was taken to launch a YouTube livestream of its decay, with the lettuce entrusted to the care of the social video editor, Edward Keeble, who took the salad item home to his flat.
Viewing rapidly grew, with Keeble adding stick-on googly eyes, a wig, drinks and a supply of sausage rolls from Greggs as the lettuce sat on a table next to a picture of the prime minister.
“Credit where it’s due, the person tasked with getting the lettuce and babysitting it has really added on and kept the interest. Everything from the Saturday night disco lights to the ProPlus and the Irn-Bru,” said Livesey.

The earliest occurrences of the phrase to give credit where credit is due and variants that I have found are as follows, in chronological order:

1-: From a letter to Henry Flood, by ‘Thuanus’, published in The Dublin Evening Post (Dublin, County Dublin, Ireland) of Thursday 9^th January 1783:

I say, that you were for a long period, not only the ablest defender, but also the actual mover of the Limitation Bill, in that very session of Lord Townshend, when it passed into a law.
I say also, that in the same session, when the Octennial Bill came over altered, and the enemies of it hoped to throw it out on that principle, (though they were every day passing altered bills of a less beneficial nature) you moved an Address of Thanks to the King and to Lord Townshend, for its return, and thereby put an end to all opposition to the bill; instead of opposing Lord Townshend, you appeared in this to have been ready to give him credit where he deserved it: nor did you oppose Lord Townshend, till long after, viz. after his unconstitutional protest and prorogation, when no man will deny, that by that measure, and the corrupt accumulation of new offices, he deserved all manner of opposition.

2-: From Friendly Hints relative to the modern practice of Physicians, by ‘an Old Patient’, published in The Bath Chronicle (Bath, Somerset, England) of Thursday 22^nd March 1792:

Women, especially old ones, are quacks. These must be humoured; by no means contradicted, at least abruptly. Partly by gratifying their vanity, partly by surprising them by divulging some nostrums as wonderful arcana, those physicians who have the most knowledge of the world, and the best talents for pleasing, will ingratiate themselves into the good opinion of females; when men of profound learning, but aukward [sic] manners, will be neglected. On these occasions, the nurses are entitled to their share of adulation. The fact is, that a case that requires great penetration does not occur once in a hundred instances; and nature being left to herself, a physician often acquires credit where no credit is due.

3-: From an article about the objections to the signing in London of the preliminary articles of peace between France and Great Britain, published in The Sun (London, England) of Tuesday 13^th October 1801:

We repeat, that it is not a question whether France or Great Britain has gained most Territory by the War?—The question is, whether we could have avoided the War?—Whether those who have conducted it have made the most of the means which were placed in their hands?—And whether, while every surrounding Nation has suffered from the contagious Principles of the French Revolution (Principles which are now in that Country giving way to more temperate, rational, and practicable doctrines), this Country has not come out of the Contest, not only without the loss of her Constitution and her Independence, but with increased Possessions, with Honour and with Glory?
It is upon these grounds that neither the Reputation of the late Administration will suffer in having carried on the War, or the present Administration in having, when the first favourable opportunity arose, thus honourably concluded it. Factious Men, we know, will cavil, and we expect it; but the fair and thinking part of the People will give credit where it is due, and will think that both Mr. Pitt and Mr. Addington have deserved well of their Country.

4-: From a letter to the Editor, by ‘Consistency’, published in the New-York Evening Post (New York City, New York, USA) of Tuesday 8^th February 1803:

SIR,
I cannot but express my astonishment at your observations on the President’s Speech and his Communications to the national legislature. You surely Sir, do not advert, to the Speech delivered at his instalment March 4^th, 1801, at the city of Washington.—Did he not then clearly and explicitly state to the nation, his inability to discharge the duties his high station required of him? and has he not, in every stage of his administration, clearly proved that he then appeared fully to appreciate his own talents, and to differ in opinion with his friends who placed him there on a false calculation that he was competent to administer the affairs of the union, better than his predecessors or any other citizen? For shame, Sir! give credit where credit is due; cease to find fault with the President.

5-: From Political Extracts, published in The Sprig Of Liberty (Gettysburg, Pennsylvania, USA) of Thursday 14^th November 1805:

It is amusing to see what pains are taken by the federalists to whittle away the glory that naturally attaches to the American name, and particularly to our rulers, for their prompt and efficient attempt to curb the insolence of the Tripolitans. […] The bravery of our tars petrified with astonishment the slaves of Mahomet. Thus did the Americans by their prowess gain an honourable peace, and which will perpetuate to fame, the names of those who were the happy instruments in bringing it about. But yet the devotees of federalism are not satisfied. President Jefferson had a hand in the business, that in their opinion is enough to curse any thing; he, in their estimation, can do nothing right; but perhaps the impartial and informed citizens who enjoy the blessings of a moderate and patriotic administration will give credit where credit is due.
Boston Chron.

6-: From Cobbett’s Weekly Political Register (London, England) of Saturday 24^th May 1806—William Cobbett (1763-1835) was an English author and political reformer:

The Chancellor of the Exchequer, who has now confessed the existence of these shameful abuses, knew nothing at all of them until Mr. Robson made his motion, a fact, I think, quite sufficient to convince you of the great danger that would arise from “delegating” the powers of inquiry to boards of Commissioners. I wish to give credit where credit is due; and I do sincerely believe, that, until the motion of Mr. Robson led Lord Henry Petty to inquire, he knew nothing at all of the abuses we are speaking of.