Something that is completely different from something else.

विपरीत

English Usage: The opposite of love is hate.

Hindi Usage: प्रेम का विपरीत नफरत है।

Located across from or facing something else.

समक्ष

English Usage: They live on opposite sides of the street.

Hindi Usage: वे सड़क के समक्ष भिन्न पक्षों पर रहते हैं।

In a manner that is contrary or different to something else.

विपरीत तरीके से

English Usage: She acted opposite to what I expected.

Hindi Usage: उसने उस तरीके से काम किया जो मैंने उम्मीद की थी।

To disagree with or resist something.

विरोध करना

English Usage: He decided to oppose the new policy.

Hindi Usage: उसने नई नीति का विरोध करने का फैसला किया।