However, you could express the idea of greater or least happiness using these options:
Comparative:
* More happily: This indicates a higher degree of happiness.
* Happier: This is a more natural and common way to express a higher degree of happiness, but it refers to the person or thing experiencing the happiness, not the manner in which they are doing something.
Superlative:
* Most happily: This indicates the highest degree of happiness.
* Happiest: This is a more natural and common way to express the highest degree of happiness, but it refers to the person or thing experiencing the happiness, not the manner in which they are doing something.
For example:
* "He sang more happily than she did." (Comparative)
* "He sang happier than she did." (Comparative, referring to the person)
* "She sang most happily of all." (Superlative)
* "She was the happiest singer of all." (Superlative, referring to the person)