The phrase 'has not relented' is a correct and usable in written English.
You could use it in a sentence such as: "The torrential rains have not relented, so the drought continues."
His aunt has not relented.
But the movement has not relented.
In short, the enemy has not relented, and significant armed violence continues.
The Kansas State defense has not relented to Texas Tech's efforts to spread the field.
Trump has not relented, framing the issue as one of patriotism rather than of players bringing attention to what they consider social injustice.
The White House has repeatedly emphasized that the system was not intended to be used against Russia, but the Kremlin has not relented.
His campaign of ire hasn't relented with quite the withering speed of his influence over the years.
UFPJ offered to put up a bond to pay for potential damages, but the city hasn't relented.
Now that the show has opened, Ms. Wells said, her routine, at least on weekends, hasn't relented.
You'd think that following that episode fans would give her a bit of a break, but the Cersei hate hasn't relented.
The Administration hasn't relented, however, and RE-ENERGYSE is back in the new FY2011 budget request now on its way to Congress.
