what is its storyline?
It is about Wade Wilson who hunts the man who gave him mutant abilities and a scarred physical appearance, becoming the antihero Deadpool.
Deadpool (film)
 In the film, Wade Wilson hunts the man who gave him mutant abilities and a scarred physical appearance, becoming the antihero Deadpool.

who starred in marvel's 2016 movie deadpool Ryan Reynolds
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Deadpool (film) [SEP] Introduction
A sequel, "Deadpool 2", was released in 2018 to similar critical and commercial success. Following the acquisition of Fox by Disney, a third film is in development at Marvel Studios (with Reynolds reprising his role) as part of the Marvel Cinematic Universe.