Avril Lavigne's Ex Gets NICKELBACKED in Halloween Diss-Fest

10/29/2012 3:45 PM PDT BY TMZ STAFF
Deryck Whibley tried to drop a Halloween insult on his ex-wife Avril Lavigne -- but ended up getting verbally slayed by Chad Kroeger ... which is about as humiliating as knowing the lyrics to "Photograph."

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