Step 1: Understand the meaning of "Mild."
The word "mild" refers to something gentle, not severe, or extreme.
Step 2: Analyze the options.
- "Laugh" is an action and doesn't relate to the meaning of "mild."
- "Pure" refers to something clean or untainted, which is unrelated to the antonym of "mild."
- "Light" refers to something not heavy, but it doesn't directly oppose "mild."
- "Severe" means something intense or extreme, making it the direct opposite of "mild."
Step 3: Conclusion.
Thus, the correct antonym for "mild" is "severe."
Final Answer: \[ \boxed{\text{The antonym for 'Mild' is 'Severe'.}} \]