Rift lake or the whole continent?
Of all of them, good candidates are buttikoferi, jewels (especially 5 star general), auratus, kenyi, and red zebra.
And kribs when they breed. Like convicts when they do. They claimed half of a 60 gallon and killed a rainbow shark.
Whole continent. Imo kribs weren't that bad ime. Similar to blue rams, but I guess it varies fish for fish. I'd say buttikoferi is the most powerful for sure as well as some other large tilapines
Never kept 5 star generals but they deserve to be up there as well as polleni sp Andapa just based on reputation. From what I've heard from polleni keepers, the smaller small spotted form isn't as aggressive as Andapa and could even be kept in species groups. Even small jewels can be aggressive too but I'd say fasciatus is the worst.
Of rift lake cichlids, melanochromis should definetely be up there. The scary thing is that auratus is one of the smaller members of the genera and the other species are larger and even more predatory. Chipokae can get to 7" in aquaria and share the same nastiness as auratus. Then there's Melanochromis Kaskazini, also known as Melanochromis sp 2, northern blue, or giant black and white auratus which gets even larger than chipokae in the wild and much more heavier bodied. I don't have much experience with this fish as its only present in the european hobby, but from what I read, it isn't as psychotic as auratus or chipokae in that they usually tolerate peaceful fish and even subdominant males which have a different coloration from the one dominate male.
However, being a melanochromis, they can easily run a tank full of any of the big malawi bruisers. They won't preemptively show aggression, but I've read reports of them easily dispatching tough challengers such as Aristochronmis and large metriclimas like Zebra Chilumba and Crabro once threatened.
I think some tanganyikans should get credit too such as Telmatochromis, Lepidolamprologus, and the larger neolamps. Brichardi especially since they can gang up on larger fish. That being said, I feel their aggression pales in comparison to the top tier malawi fish like auratus, crabro, kenyi, zebra chilumba, chipokae and is more on par with a mid tier mbuna such as red zebra, maingano, or hongi.
While buttikoferi and similar tilapias are strongest in absolute terms, I would have to vouch for either hemichromis fasciatus or melanochromis kaskazini/chipokae as the strongest pound for pound. Both fish not only have powerful dentition but are also fast and agile fish that can outmanuever slower and more brutish opponents. I might give the melanochromis an edge but only because I am biased and my auratus was a monster.
Here's a pic of a dominant sky blue male kaskazini and a subdominant male which adopts a much different coloration. I believe females are a lighter blue but retain the two dark stripes.
