Well last time I went solely by Roman numbered power levels (Class I being weakest, V being strongest)

But now I'm considering doing both classification via strength (may or may not remain the same) as well as classification via power type (probably with colors)

So I imagine it'd go something similar to: Class V Type-Black or something like that.

Also I'd still have to write up general stuff, but that's more or less unrelated to the point.