My rutilan male and female will tear each other up before mating. They are very rough when courting.
My Betta ideii pair do hate each other and have to be separated as the male tries to kill the female. However, they are known to be aggressive so it wasn't unexpected.
My albimarginata are some of my favourites and are so gentle and shy. They are easy to breed and mine have 20 odd fry that I'm looking after.
Wild splendens are more aggressive than other species, and I assume they just bred for that trait and culled/released any fish that didn't display the necessary aggression.
I love my wilds, even if half the time all I see is an empty tank because they're off hiding.