i have kept red tailed catfish and mystus wykii. in separate tanks.
the red tail quite happily lived with other fish such as cichlids, eels etc and his only crime was to try and eat the heaters and a few tank mates got eaten whole, but they were a bit too small.
the wykki on the other hand killed every single tank mate i tried so i gave up and kept him in his own. It just chased and continually bit them until they gave up and died. The wykki had the biggest death count so i would go with the wykki being the most aggressive.
But if youve got one in 50,000 gallons its probably got a teritory of 5,000 gallons so it probably would feel the need to defend its territory so much.