This gives you the developpers' own view on who is in each power category.
Feel free to comment on what seems coherent with the story or what seems incoherent with the power scaling you have in your head.
A FEW NOTES AND DISCLAIMERS:
✮ This is the developers' own view for this game and is not an official statement such as the ones you can find in official guidebooks of the franchise.
✮ While you can see who are in higher or lower categories, characters in a same category are classified without power comparison, in the order of the character selection screen. So Goku has Super Saiyan 3 and Super Saiyan God belonging to a same category, but it doesn't mean they are stated as equal in power, since Super Saiyan God is obviously more powerful than Super Saiyan 3 story-wise. It just means that for the devs, despite one being stronger than the other, they still belong in a same power level category.
✮ Despite the developpers' best intent to show something coherent with power levels story-wise, there's still gameplay to take into account, with other forms and how to balance things out with the costs. So they might have taken a character a step up or down compared to what you would logically envision for them.
✮ Because pictures can't always represent clearly the characters or forms (especially with multiple versions of some characters depending more on the timeframe than on any distinct appearances), the names also appear clearly in text form below the pictures so that you can clear out any doubt.
LEVEL 10 ✮ UNFATHOMABLE AND UNDEFEATED
Spoiler:
LEVEL 9 ✮ NEAR-SUPREME
Spoiler:
LEVEL 8 ✮ DIVINE THRESHOLD
Spoiler:
LEVEL 7 ✮ NATURAL MORTAL POWER LIMIT
Spoiler:
LEVEL 6 ✮ BEST AMONG MULTIPLE WORLDS
Spoiler:
LEVEL 5 ✮ PLANETARY THREAT
Spoiler:
LEVEL 4 ✮ GAME-CHANGING ASSET
Spoiler:
LEVEL 3 ✮ EXTRAORDINARY MORTAL
Spoiler:
LEVEL 2 ✮ UNUSUAL POWER-WIELDING MORTAL
Spoiler:
LEVEL 1 ✮ CASUAL MORTAL FIGHTER
Spoiler:
The one thing I don't understand about these is why Cell is so high, yet the man who defeated him, Mr. Satan, is so low. It shows how little attention these developers pay to the source material. I'm sure someone will get it right one day.