The word root mal means "bad, badly." The suffix -ous means "having the quality of."
In which sentence is the word malicious used correctly?

We will meet, discuss the malicious, and then vote on the best option.

Be careful not to malicious when you are talking with someone and hurt their feelings.

The chef served a malicious meal, so the reviewer gave the restaurant five stars.

Angry and defeated, he began spreading malicious lies about his opponent.