An antonym of an unambitious assistant would be an "ambitious assistant." While an unambitious assistant may lack drive or initiative, an ambitious assistant actively seeks to achieve goals, take on challenges, and contribute significantly to their team's success. This contrast highlights the difference in motivation and proactivity between the two.
The opposite is ambitious, which can mean motivated, determined, or can have the connotation of ruthlessness.
nothing
principal
Unambitious
unambitious
Lazy or unmotivated (unambitious).
The opposite could be insincere, or (for enthusiastic) unenthusiastic or unambitious.
unambitious
Examples of words ending with 'tious' are:ambitiouscautiousconscientiouscontentiousdissentiousexpeditiousfacetiousfictitiousflirtatiousinfectiousnutritiousostentatiouspretentiousrambunctiousrepetitiousscrumptiousseditioussurreptitiousvexatious
The closest word I can think of is "unambitious."
The antonym of the word 'synonym' is 'antonym'.
An antonym means "opposite". So an antonym for the word synonym is antonym.