Do your worst
Definition 1 of 1
Pro Tip 1/3Defiant Challenge
Used when someone is unfazed by threats and defiantly invites the challenger to give their best shot. 
The boxer sneered at his opponent and said, 'Do your worst; you won't knock me down.'
Pro Tip 2/3Sarcastic Taunt
Can be used sarcastically to mock someone's attempt to harm or intimidate, implying it won't be effective. 
He laughed in the face of the dire movie reviews, saying, 'Do your worst; I'm still going to watch it.'
Pro Tip 3/3Emotional Resilience
Shows a strong emotional stance, indicating readiness for whatever negative comes one's way. 
She stood firm during the heated debate and declared, 'Do your worst; I can handle it.'