The word "un-excessive" itself means not excessive or moderate, so the antonyms would be related to extremes of quantity or quality. Possible antonyms for "un-excessive" could include "excessive," "extreme," "overindulgent," "outrageous," "overboard," "overdone," "lavish," "exorbitant," and "immoderate." These words indicate a situation where there is too much of something, either in terms of quantity, quality, or intensity. For example, an excessive amount of sugar in a dessert can make it taste too sweet and overpowering, while an immoderate amount of alcohol can lead to drunkenness and other health problems.