User blog comment:Bratpack/Miscellaneous/@comment-112155-20141228144724

Intelligence uses its own classification:
 * 1) Slow/Impaired
 * 2) Normal
 * 3) Gifted
 * 4) Genius
 * 5) Super-Genius
 * 6) Omniscient

I don't think the MCU has portrayed any "Super-Genius" or "Omniscient" intelligences, that would be for entities such as the Kree Supreme Intelligence or god-like entities.

People like Banner, Stark, Fitz, Simmons should use Genius, and "clever" people like Black Widow should use "Gifted"