^ I am talking about that thread too. Any fish can be monster but then again its all people's opinions. It is pointless to see which fish are labelled as monster as monster can mean anything (monster sized, monster predatory, monster aggressive etc..) Even guppies can be monster too as you have ugly fancy strains and few see thru guppies.
If you want mini predatory fish that eat full grown guppies or if you want mini super aggressive fish who like abuse other fish then just say specifially instead of use mini monster.