Important means anything that is valuable or substantial, other words that convey the same meaning would be crucial, critical, imperative, urgent, essential, etc... Antonyms would be non-essential, meaningless, trivial and optional.
Cooliousis
uninteresting
high up!!!
You might be able to use words like 'left', or 'departed'.
However, instead, on the other hand, except, besides, nonetheless, otherwise, although, despite the fact, meanwhile & although
two
you are not
rather, preferably, alternately
since
Abscond.
uninteresting
Cooliousis
Special?
execute
Thou, ye, thee
Artillery,Armory
It is preferable ...