Animal-like: Beings who are mainly instinctual, lacking intellectual process for the most part.
Very low: Essentially mentally challenged individuals.
Low: Beings who could be classified as "dumb" in comparison to the average human.
Below average: Young humans or below average adult intellect.
Average: Average human intellect.
Above average: Above average human intellect.
High: High human intellect.
Very high: Borderline genius human intellect.
Genius: Genius human intellect.
Super genius: Geniuses amongst geniuses, essentially anything above overall 200 IQ. A few human outliers in real life might exist somewhere around this range, but this is essentially the start of superhuman intellect.
Hyper genius: Geniuses whom are essentially super computers.
Cosmic genius: Geniuses of cosmis proportions whom can borderline seem nigh omniscient or capable of competing with nigh omniscient beings through sheer intellect. This is likely the scarcest category of all in fiction.
Nigh omniscient: Has cosmic amounts of mental capacity.
Omniscient: Posseses an absolute mind, all knowledge.