Possible Clues:

• With malice
• In a wicked manner
• How villains behave
• Extremely wickedly
• In a wicked way
• Could be lively, but not at all well
• In wicked or depraved way
• The way to the start of 16 across
• In such a bad way one might get lively
• That makes one lively in the way of 18 down