- Both in their most powerful/prime state
- In character
- Random encounter
- No BFR, win by KO or death
Can't Amaterasu use wind to literally spin an entire galaxy? Or, you know, reality warp a sun into existance?
I don't know much about Aslan, apparently, but I'll just say Amaterasu for the simple sake of not caring (BTW, Semi-Omniscient doesn't mean much in a direct battle...Okay, screw me. I don't care.).
See, it's the In-Character requirement that tips the scales. Aslan is Lawful Good. He straight up says in The Voyage of the Dawn Treader that he obeys his own rules. And he doesn't seem to allow much in the way of interference. The only display of his powers is when he creates the world. After that, he behaves like a lion in battle.
Amaterasu is Chaotic Good and she has no qualms about rewriting reality when she feels like it. Hell, she moved the sun for no better reason than to dry a little old lady's clothes faster.
So Amaterasu's got this one in the bag.