Hmm, Ares and Acala have their Awakenings, but I can't see them as being particularly useful for you. SSR Beelz is pretty funny, but not sure if it's worth paying for. Prometheus can be useful if you ever need to delay content, but with Belial, I doubt you'll need that...

So either Amaterasu (for comfort farming, though Yamaraja largely fulfills the same role) or somebody in Thunder for fighting through Water content (probably Athena). But I don't see any major upgrades for you.