For Dragon Quest 1-3, the cast are currently scaled from
this feat and Malroth flying from one country to another in seconds for speed. First looks like a game mechanics, but the second might be fine. For tiers, the scale from Rubies creating Torland, which is basically a Pangea like Continent sealed in some "Alternate World". That's where the
High 6-A ratings come from. Scales to all the protagonists and end game bosses of all three games. Erdrick does have a low end keys where he fights building sized monsters at the beginning of the game. And Mid game also Orochi's nuking a town via volcano eruption statement.
Dragon Quest 9 Hero and Corvus scale from Corvus flying at
Massively FTL+ speeds, which is good. There's
this feat and Galaxy Rang "Gashing Galaxies" for the
4-A ratings, but it sounds vague. But at the very least, Corvus turning to the biggest and brightest star in the sky is a solid
High 4-C feat. Zenus creating every star in the sky is definitely Tier 4, but unsure about
4-A.
And for Dragon Quest 4 to 8 (Which I haven't played 5-8 so I don't know too much)
The Goddess (Dragon Quest) created the entire Dragon Quest Multiverse is why she's
2-C. And she's also Omnipresent across Space-Time.
Estark is comparable to the Goddess and also has a statement of "Transcending all Dimensions, time and Space". Which is where his
Immeasurable speed comes from. Necrosaro is superior to Estark and Estark does appear in multiple games. And there are statements about other characters being comparable to the goddess, so whoever's comparable to her would be
2-C and
Immeasurable by the looks of it.
That's what I got at the top of my head.