Not my list. Found it online a few years back and saved it.
1) Nandopsis beani - if you've ever seen or spoken to a very knowledgeable keeper on these, you'll agree that NO other cichlid flips out like this one does. I've heard stories of foot long specimens taking 600g for themselves. Now THAT is impressive.
2) Caquetaia umbrifera - a 2-3 foot fish maybe, but 1000g of space is ALOT of tank regardless, and usually it takes MORE than that to house a mature male umbie with tankmates
3) Parachromis dovii - the infamous wolf cichlid, not overrated and still a VERY nasty fish that even at only 1.5-2 feet can still take up a tank of easily 500g, usually 600 or more.
4) Nandopsis haitiensis - one of the most underrated cichlids as far as aggression goes, this fish is literally black hell. At only 14 inches, a large male could quite easily take up more than 200g for itself.
5) Amphilophus festae - basically the red version of N. haitiensis when it comes to aggression. I would have given the average festae a tie with the average haiti, but festae are very wimpy until they hit a certain size (differs for each specimen IME), but still a big fish with one of the nastiest tempers around.
6) Neolamprologus Christyi - easily the most aggressive african cichlid. Attaining an average length of 3-5 inches, I know of several keepers who kept them in tanks upwards of 75g and still had them slaughter tankmates. Another account tells of them killing a colony of neets that were previous tankmates. NOT a fish to be messed with.
7) Parachromis motaguensis - another underrated cichlid, very nasty guapote with teeth to back it up.
8- Nandopsis istlantus - hyper aggressive and nasty despite its small size. Sheer temper problems with this fish.
9) Nandopsis salvini - IME they've been jsut about as nasty as the average istlantum, but again, there seems to be more variation in temperment with this fish (I've heard of a few tame sals, but ever of a tame istlantum). Still a contender though.
10) Nandopsis grammodes - I've heard of these fish taking down istlantum and salvini, and judging by the equipment and the temper I don't doubt it. However, I've heard of alot more tame grammodes than either salvini or istlantum.
11) Herichthys bartoni - another underrated cichlid, which from what i've seen/heard is just about as nasty as the grammodes/istlantum/salvini trio. If grammodes = mini dovii, istlantum = mini umbie, and salvini = mini trimac, then bartoni could pass for mini haitiensis.
12) Hemichromis fasciatus - IMO one of the most overrated fish for aggression... I've heard of them killing buttikofferi in the wild though so I think they deserve a spot on this list, but not as high as most people would think.
13) Nandopsis urophthalmus - a VERY VERY VERY underrated guapote type cichlid. They're quite possibly one of the most tenacious cichlids out there, and tend to be very consistent in temperment.
14) Melanochromis sp. "giant pike/giant black and white pike auratus" - the largest of the melanochromis, both attaining near 10 inches, with a temper to match. Easily the most aggressive mbuna, and even giving neolamp. chrysti a run for worst temper of the africans. If you thought auratus or chipokae were bad, this fish will blow you out of your seat. They're even worse than M. melanopterus.
15) Amphilophus saggitae - commonly called "black demon" cichlid. Deserves every letter of it, being worse than its close relative amphilophus citrinellus.
16) Amphilophus zaliosus - the most aggressive of the RD complex, super nasty hyper charged fish. Too bad it only reaches 8 inches.
17) Amphilophus trimaculatus - a well known bruiser, VERY high on the top toughest, but I've noticed ALOT of variation in the temperment of this fish. However, if more trimacs were as aggressive as they're generally seen, I'd put them after motaguensis.
18- Amphilophus citrinellus - I had a hard time deciding whether this fish should come before or after the trimac, but I decided after. Still, expect about the same level of roughness as a trimac with a few more exceptionally well behaved specimens
19) Crenicichla strigata "venezuela" - the largest pike cichlid, and consequentially the most aggressive. Nasty fish, will usually attempt to kill any tankmates it is capable of overpowering.
20) Amphilophus labiatus - another very aggressive cichlid, but much more variable in temperment than the rest of the RD complex. Still, a very aggressive fish which demands close attention when tankmates are incorporated.
21) Neetroplus Neematopus - little speed demons, very nasty fish capable of encompassing a large territory. However, many specimens are peaceful until breeding, so they get a lower rating than alot of other cichlids.
22) Tilapia buttikofferi - a very capable fighter and all round tough fish that could easily make the top 15 or even top 10 toughest cichlids, but IME overrated for actual aggression. It has been my experience that if kept in good sized tanks, they aren't too aggressive unless the other fish initiates the fight.
The other list
1. Parapetenia Dovii - a.k.a. wolf cichlid
2. Petenia Umbrifera - a.k.a. blue-freckled monster
3. Parapetenia Managuensis - a.k.a. jaguar guapote
4. Nandopsis Haitiensis - a.k.a. Haitian cichlid
5. Tilapia Buttkoferi - a.k.a. hornet tilapia
6. Amphilophus Citrinella - a.k.a. Midas cichlid
7. Parapetenia Motaguensis - a.k.a. red tiger cichlid
8. Amphilophus Trimaculata - a.k.a. three-spotted cichlid
9. Parapetenia Beani - a.k.a. green guapote
10. Parapetenia Friedrichsthali - a.k.a. yellowjacket cichlid
honorable mentions: aequidens rivulata (green terror), amphilophus atromaculata (rust-bellied cichlid), amphilophus festae (red terror), amphilophus labiata (red devil cichlid), amphilophus lyonsi, amphilophus salvini (yellow-bellied cichlid), amphilophus urophthalma (orange tiger cichlid), amphilophus zaliosa (arrow cichlid), archocentrus octofasciata (Jack Dempsey), astatheros macracantha (high-backed cichlid), astatheros robertsoni (emerald cichlid), hemichromis fasciata (fire-throated jewelfish), herichthys carpintis (pearl-scaled cichlid), herichthys cyanoguttata (Texan cichlid), herichthys minckleyi, herichthys pearsei, nandopsis ramsdeni, nandopsis tetracantha (Cuban cichlid), parapetenia grammodes, parapetenia loisellei, parapetenia steindachneri, petenia kraussi