The term "mitigate" denotes a reduction in severity, seriousness, or pain. An antonym is a word with an opposing meaning, thus signifying an increase in severity or intensity.
- Intensify: This word signifies making something more intense or severe, directly opposing "mitigate." Hence, "intensify" is the correct antonym.
- Lessen: This word means to reduce in extent, amount, or degree, making it a synonym of "mitigate," not an antonym.
- Avoid: This pertains to keeping away from or refraining from an action. It does not directly relate to severity or intensity, thus not a direct antonym of "mitigate."
- Settle: This means to resolve or reach an agreement or decision. While related to resolving conflict, it is not the direct opposite of mitigating.
Consequently, "intensify" is the word that means the opposite of "mitigate."