In Episode 8 - Black and White Sword Dance, after Kirito got Asuna to agree to cook the Ragout Rabbit, Asuna dismissed Kuradeel and got refused:
Kuradeel: I can not leave you alone with a shady character like this
Asuna: While I can't say anything about his shadiness, he is actually quite strong. In fact, he's 10 levels above you, Kuradeel.
Kuradeel: Are you implying that I am somehow inferior to him? Wait, don't tell me he is one of those Beaters.
In Episode 2 - Beater, after beating Illfang the Kobold Lord, Kirito was discovered as a Beta player. Reflecting on Diavel's request, Kirito takes an antagonist stance and lies about how far he had progressed during the beta of SAO:
Kirito: I made it to floors not even the other Beta players could reach.
Kibaou: Then that makes you worse than a Beta, YOU A GODDAMN FILTHY CHEATER.
Background Player: He's a Beater!
Kirito: Beater huh? Yeah, I like the sound of that.
I was under the impression that Kirito was the only "Beater". However, Kuradeel says one of those Beaters, which implies that there are more as apart from him. Using the plural form, Kuradeel is grouping Kirito with others.
So I am wondering, were there any other Beaters in SAO? If there were, do we know who they were?