οἷος ὢν τῷ μὲν ἥδιστος, ἑαυτῷ δὲ βλαβερώτατος ἂν εἴη
All the older editions have an here as indicating a potential optative. The recent edition 2011 by Harvery Yunis, omits an, making reference to Cooper’s Grammar 54., 3., 11. I wonder what is written there, I can’t find it online. According to Smyth, pot opt cannot be used without an in Attic prose.