> {}{}{}{}… {}{}
You are reading the part the other way around. The one who has been beaten is the speaker and the one who beat the speaker is (or someone from that gym).
means **** , which is what the speaker refers to by . is certainly often translated as "everyone", but that is only the " ** _figurative everyone_** ".
In reality, is used when more than one person are doing the same (kind of) thing. Furthermore, in emphatic or exaggerated speech, we quite often use to refer to just one person when we have a strongly negative feeling about his/her action.
> Could you also confirm that is the subject of ?
Exactly, it is. is the only "real" verb there since is used within a relative clause.