Honestly the most aggressive tetras I have found are the ones with distinct sexual dimorphism
One exception is serpae tetras which have no distinct sexual dimorphism but can be aggressive and nippy toward other fish so I am sure there are other exceptions as well.
Is it correct to say that slender body tetra, lacking sexual dimorphism, are generally non aggressive? Tall body tetra, sexually dimorphic, are generally aggressive. Non-aggressive tetra are generally good schooler/shoaler because males don't break out to fight one another.
There are exceptions to the generalization, such as:
Silver tip tetra, slender but aggressive.
Amber and Lemon Tetra, tall but non-aggressive
I am sure you can identify more to the exception.
Serpae tetra is not an exception, aggressive and sexually dimporhic. Male dorsal fin is darker than female.
Not sure if bleeding heart is an exception as I got conflicting opinion on their aggression.
It is unfortunate that most peaceful tetra are small, bait fish like that are unsafe to coexist with angels and bigger tankmates.