Roman gladiators come to mind. They could be extremely popular with the masses but still be disreputable just like rock stars today. The most popular would be portrayed on objects like this glass cup in the Metropolitan Museum of Art or this mosaic. One gladiator, Tetraites / Petraites, is on this cup and was mentioned in Petronius’ Satyricon.

And they could engage in what we might think of as ‘rock star behaviour,’ such as having many female groupies. This was a common topic of satire and gossip but also probably had some basis in fact. Juvenal wrote about a senator’s wife who ran off with a gladiator, and there other such rumours about powerful women, but much of this was probably untrue slander. Still, they seemed to have been admired by women. A bit of graffiti in Pompeii claims ‘Celadus the Thracian gladiator is the delight of all the girls.’