Festaes, tilapia buttikoferi, pike cichlids, flowerhorns, umbee, jags, dovii...
Red devils are up there but there's def bigger badder cichlids on the block that can withstand the red devils aggression. But of course, always depends on the individual fishes personality and the sizes of the fish. I'd say festaes, butti's, or jags probably the best option due to size. I haven't personally done anything with regular jacks but I know they can hold their own also. U might wanna jump on youtube and look up some red devil tanks and see what guys are mixing together. It's always a hit or miss game with the aggressive fish mixing so at least that'll give u some hope that whatever u try could possibly work.
PS I've got 6 electric blue jacks and they are sissies, I would never advise them with one of the bad boys of the cichlid family. They're more of a semi aggressive community fish with like characins or rainbows and such.