Titan Luz is easily the strongest one of them due to her limitless Titan Magic

Gus is on the second place. Even if someone is able to resist his "trauma bomb" he is able to read his enemy's mind to pull an Grom

Third place goes to Willow due to her raw power

Amity and Hunter are pretty equal but I would put Hunter above Amity because he was trained in the Emperor's Coven since he was created

And Luz is the weakest one of the Hexsquad (if we don't count vee). She has much magical knowledge but that's totally useless when she can't do anything against an opponent in the Human realm or after the Monarch's death