Power rating is considered the total stat points of all 6 attributes multiplied by the ascension of their destiny. It is temporary destiny x permanent destiny x tier.

Power is not absolute, as the effects of abilities influence the outcomes in battle. So power is just a means to categorize people based on potential danger. 

No. Rank: Total Stat

0. Unranked: Less than 1,000.

1. F: Above 1,000 (Thousand Mark).

2. E: Above 10,000.

3. D: Above 100,000.

4. C: Above 1,000,000 (Million Mark).

5. B: Above 10,000,000.

6. A: Above 100,000,000. 

7. S: Above 1,000,000,000 (Billion Mark).

8. SS: Above 10,000,000,000.

9. SSS: Above 100,000,000,000.

10. X: Above 1,000,000,000,000 (Trillion Mark).

Note that this doesn't take into account the power of Demigods.

Power rating and ability form the bulk of the power of a super. As for abilities, they are divided into Omega, Alpha, and Beta which depends on how well they scale with power rating.