Jack says that “Leona’s magic is way more powerful” than his, Deuce’s and Ace’s (more: Leona’s Power).
Leona says he “aced (his) protective magic classes in (his) sleep,” possibly insinuating that defensive magic is a particular strength of his.
This may tie in to Book 6, where we see Leona utilize a magic barrier to protect Ruggie from falling glass when CHARON invade the school, and setting up a barricade during Playfulland.
While nothing is stated aloud in dialogue it is visually insinuated that Leona protects Deuce from a magical attack in Book 7.
Much like Vil, Rook, Epel, Azul, Riddle and Jamil he uses an unspecified form of attack magic to blast cages open during Book 6.
While never described explicitly in dialogue, based on visuals and sound effects Leona may have used some form on attack magic on the dream-version of Kifaji in his Book-7 dream.
In another clash in his dream of Book 7 Leona seems to use magic to destroy a hologram.
Leona also levitates Ace to safety during the Playfulland event (tossing him into Cater’s arms), and uses clothes-changing magic at least three times: in a vignette, Book 6 and Book 7.
Leona mentions a magic spell that re-attaches detached buttons to clothing, and while it is possible he did not actually cast any such magic in the vignette where it is mentioned, that might also be something that he is capable of.
Twisted Wonderland Reference Note 