Is there a word for "the use of opposite expressions" similar to "comparison"

https://en.m.wiktionary.org/wiki/apagogic

apagogic (not comparable):

(rhetoric) Proving indirectly, by showing the impossibility or absurdity of the contrary.

https://en.m.wiktionary.org/wiki/apagoge

apagoge (countable and uncountable, plural apagoges):

(logic) An indirect argument which proves a thing by showing the impossibility or absurdity of the contrary.

Disclaimer: literally nobody has ever heard of these terms

When used as a debate tactic you would refer to it as "reductio ad absurdum"