This is the 3473rd most frequent Russian word.
противном
"Противном" is the dative or prepositional form of "противный," meaning "disagreeable," "nasty," or "opposite" depending on context.
Here, "противном" ("opposite") refers to an alternative scenario or condition that differs from the current one.
Он поступил неправильно, и в противном случае я бы его поддержал.
He acted incorrectly, and in the opposite case, I would have supported him.
In this sentence, "противным" ("disgusting") describes something unpleasant or distasteful.
Этот запах был слишком противным, чтобы дольше оставаться в комнате.
This smell was too disgusting to stay in the room longer.
Here, "противном" ("opposite") denotes location or placement on the opposite side relative to the speaker or subject.