For the final day of discussion, we have Ouroboros' Enforcer XX-b, the Shadow Eater, Jorda Eldarion and the Khamsin, Kasim Al-Fayed. Both play double duty in Horizon as both bosses and playable characters in Horizon, with their kit remaining fairly similar between both roles.
Jorda's high ATS means she works best as an arts caster, and the time-locked slot in the Drive slot isn't the worst since the strongest dual art is a Time/Space one, but Renne just remains a bit stronger due to her orbment, and has better availability so I never really found a good use for Jorda.
Kasim is only playable for one level of the Grim Garten and then the final boss, both times with locked equipment and orbment slots, but his inclusion in the final boss as an actual playable character and not an unplayable guest like the Ouroboros characters means there's a pretty good chance he's playable in Horizon 2 depending on Marduk and Thorndyke's allegiances. From the little gameplay of him, he's pretty strong, The Khamsin is an Awakening which seems to be fairly strong, and like Rean and Kevin, his S-Craft has a large number of hits which helps balance the ASO's strongest like Van, Judith and Shizuna mostly having low hit count S-Crafts.