Question's pretty much in the title. I've read it as "No friend ever served me, and no enemy ever wronged me, whom i have not repaid in full". But I've also read somewhere, honestly I think wikipedia, that Plutarch claims Sulla's epitaph said "No better friend, no worse enemy". Mike Duncan's History of Rome podcast also used this Plutarch version during his episode on Sulla. Do we know which version is the correct one? I also know that the American General Mattis has used the latter for a biography or something. Thanks in advance!
Unfortunately, we do not have his the original epitaph inscription. The information on Sulla's epitaph is given to us by Plutarch, who writes of it in Parallel Lives:
"τὸ μὲν οὖν μνημεῖον ἐν τῷ πεδίῳ τοῦ Ἄρεώς ἐστι τὸ δὲ ἐπίγραμμά φασιν αὐτὸν ὑπογραψάμενον καταλιπεῖν, οὗ κεφάλαιόν ἐστιν ὡς οὔτε τῶν φίλων τις αὐτὸν εὖ ποιῶν οὔτε τῶν ἐχθρῶν κακῶς ὑπερεβάλετο"
(Plutarchi vitae parallelae: Sulla 38, 4)
This can be roughly translated as:
"But, in any case, his memorial is in Campus Martius, and they say he left his own epigram written there, the gist of which is that none of his friends surpassed him in returning good, nor any of his enemies in returning evil."
The original Latin,which would have been written in meter, is unknown. It is difficult to figure out the exact phrasing of poems wrung through (at least) 2 translations, so they're no real "correct" version, it's all up to the translator's interpretation since all we have is the paraphrased version given by Plutarch.