No clue what Leonard wanted, maybe interactions like levers, but for you -DJ_Studios- it should be as simple as adding "Attack entities of type 'Living Entity'" with a start condition of it not being the same entity (sub)type. All mobs are considered Living Entities, even zombies and skeletons, since they use AI or require a Unique Interaction (armour stands equipping armour).
i know this is 2 years old but im bumping it because want to do this too, a creature hostile towards everything execpt itself.
No clue what Leonard wanted, maybe interactions like levers, but for you -DJ_Studios- it should be as simple as adding "Attack entities of type 'Living Entity'" with a start condition of it not being the same entity (sub)type. All mobs are considered Living Entities, even zombies and skeletons, since they use AI or require a Unique Interaction (armour stands equipping armour).