While this is not specifically a love-letter, it does involve a former Letter awardee. That's right. The Ragin' Meditteranian, The Emperor Hadrian.
This is from Dio Cassius documenting one time when Hadrian killed his rival, Apollodorus.
"Now Hadrian spared these men, displeased as he was with them, for he could find no plausible pretext to use against them for their destruction. But he first banished and later put to death Apollodorus, the architect, who had built the various creations of Trajan in Rome — the forum, the odeum and the gymnasium. 2 The reason assigned was that he had been guilty of some misdemeanour; but the true reason was that once when Trajan was consulting him on some point about the buildings he had said to Hadrian, who had interrupted with some remark: "Be off, and draw your gourds. You don't understand any of these matters." (It chanced that Hadrian at the time was pluming himself upon some such drawing.) 3 When he became emperor, therefore, he remembered this slight and would not endure the man's freedom of speech. He sent him the plan of the temple of Venus and Roma by way of showing him that a great work could be accomplished without his aid, and asked Apollodorus whether the proposed structure was satisfactory. 4 The architect in his reply stated, first, in regard to the temple, that it ought to have been built on high ground and that the earth should have been excavated beneath it, so that it might have stood out more conspicuously on the Sacred Way from its higher position, and might also have accommodated the machines in its basement, so that they could be put together unobserved and brought into the theatre without anyone's being aware of them beforehand. Secondly, in regard to the statues, he said that they had been made too tall for the height of the cella. 5 "For now," he said, "if the goddesses wish to get up and go out, they will be unable to do so." When he wrote this so bluntly to Hadrian, the emperor was both vexed and exceedingly grieved because he had fallen into a mistake that could not be righted, and he restrained neither his anger nor his grief, but slew the man. 6 Indeed, his nature was such that he was jealous not only of the living, but also of the dead; at any rate he abolished Homer and introduced in his stead Antimachus, whose very name had previously been unknown to many."
To quote the man who sent this to me: "I think he definitely showed Apollodorus that you can't put a collar on the H-dawg."
- Love Letters to Dead Architects: Revenge is a Dish Best Served Rome