stay
will not
The opposite is unfavorable, with other possible words being adverse, contrary, or hostile.
Delicate, fragile, inactive, unskilled, or incapable. Those words are the opposite of efficient.
"Worse" is the comparative of "bad". Its opposite is the comparative of "good", in other words "better".
Supreme Significant (my mind just went blank) (any help would be nice:-)
Quickly,rapidly and speedily are some of the opposite words for slowly.
Some opposite words for certainty include disbelief, doubt, and distrust.
The preposition "without" can be the opposite of "with" as in the examples: He went with his brother/He went without his brother.
Blessing
healthy
fartens
some or all reminisce
Some words do not have opposites. Astronomy is one of them.
went.
stayed?
weird
If electrons went the opposite way they might change their polarity.