I had an Osphronemus gourami that would not even look at smaller fish, but I have read of others that couldn't be trusted with the little guys. Individual personalities vary. Aggressiveness has nothing to do with this; predation and aggression are two entirely different things. A friend had a pearsei cichlid that was equally inoffensive to small fish.
I guess a lot depends upon your definition of the term "large", referring to both the fish size and the tank size. In a big enough tank, a big enough predator usually won't bother with truly tiny fish because they are simply not worth the trouble to eat. There are plenty of pictures on MFK and elsewhere showing large Arowanas, Gouramis, Wolffish, Cichlids, etc. living in large tanks with a considerable population of tiny Guppies, Neons, etc. that just swim "under the radar", so to speak. The King of DIY has/had a large tank with a single large Arowana and a huge number of Neons or Cardinals; somebody on MFK has shown their tank housing a single large Wolffish (malabaricus?) living with a bunch of Guppies. It makes for a very cool display, IMHO.
And then, of course, there are...the real jerks. My Jelly Cat lives in a 200-ish gallon tank that is plumbed together with a 75-gallon tank housing a breeding colony of Green Swordtails. The 75 acts as the sump for the system, and new-born fry regularly manage to find their way all the way to the pump which then whisks them violently up and into the catfish's domain. I just leave them alone...hey, they've gotta take responsibility for the consequences of their own choices!
...and I thought and hoped that they'd probably be okay, and would grow large enough that I could more easily spot and net them out. But...they don't. On more than one occasion I have been sitting and watching that tank, only to see a 1/4-inch Swordtail venturing too close to the wrong end of the 18-inch catfish. The big guy doesn't react at all, unless the fry comes too close...and then, just before it touches a whisker, there is that explosive GULP and the fry...along with a mouthful of plant material, a few snails, some sand and a quart of water...disappears. Then all that extraneous material is laboriously chewed and gummed and spit up a bit at a time...but the fry is gone forever.
The number of calories bound up in that tiny fish is probably 1/10 the number that the catfish expends when he does this. He is kept well-fed...but he is never sated. He's an idiot, plain and simple.
