the two I had never touched any other fish...just the normal...digging up sand, pulling the fake plants out, knocking stuff over and mine also liked to pick up rocks with their mouths and throw them at the glass...lol...they are awesome fish though!
My Oscar constantly is a bully to my smaller Birchirs and just about anything that swims in his line of vision, he gives them a subtle nip every time just to keep everyone in line.
My first monster fish was a red oscar. He wasnt aggressive in the slightest but nobody would bother him because of his size, that is until my dovii grew to about 6". At less than half the oscars size he had my red quarentined to one corner of my 210. As for distruction, all he did was dig, knock down wood, and tare out plants, they've got a strange way of redecorating.