How is “set against” used?

In Mystic River (2003), one line is: “Why are you so dead set against that kid?”

Which movie is “set against” from?

The clip at the top of this page is from Mystic River (2003).

Phrasal verb

to make sb oppose a friend, relative, etc.; to judge sth by comparing good or positive qualities with bad or negative ones

Heard in 9 movies

1
set sb against sb
to make sb oppose a friend, relative, etc.
She accused her husband of setting the children against her.
2
set sth (off) against sth
to judge sth by comparing good or positive qualities with bad or negative ones
Set against the benefits of the new technology, there is also a strong possibility that jobs will be lost.
3
set sth (off) against sth
to record sth as a business cost as a way of reducing the amount of tax you must pay
to set capital costs off against tax

Definitions from the Oxford Advanced Learner's Dictionary, 9th edition

Why are you so dead set against that kid?

Said in 8 films · #1