Well, the odds a fish under 8 inches can shatter a 40 gallon tank seem kinda unlikely, imo.
While the OP used the words "attack you", I think the greater point is, he just like really aggressive fish. To each his own. I know of no smaller species that I can think of that would have that Dovii or Jag-type of attitude I think you are referring to, on its own. As other have mentioned, there are convicts, but there attitude often comes hand in hand with breeding, which of course means they are not alone. You could always find a more aggressive one as a loner, it possible, but maybe a crapshoot. Maybe someone knows of a species I'm not thinking of right now.
Actually, now that I'm thinking of it, this isn't an SA or CA cichlid, but I'll mention it anyway, given the context of your question. I once had a lone occie that defended its shell vigorously, even with no other occies in the tank! LOL... it defended that shell to the point of attacking my siphon when I did water changes! A funny sight, coming from such a little guy!
Anyway... I know occies are pretty rambunctious africans, but I do not know if this would be typical behavior from them when kept singularly. You may have to ask about that in the Old World forum. I eventually added other occies to keep my guy company.
Good luck with your search.
-Rich