What is 剋 doing in the Cantonese translation of the movie title “Widows”?
剋 and 黑 are pronounced the same in Cantonese

剋·寡婦 is a wordplay of a common term 黑寡婦 (Black widow: 1. A woman who murders her husband(s) 2. a kind of spider) And as the title implied, it is about a widow who has 剋夫命 (Be accused of bringing bad luck that cause her husband to die)

Chinese rarely translate foreign movies titles word for word. More often than not, the Chinese writer would totally ignore the original title, and make a new one in Chinese to attract Chinese viewers.

Some good example:

Meet the Fockers --> 非常外父智擒霍老爺 (sounds funny)

Wedding Crashers --> 冒牌伴郎智擒姊妹團 (sounds funny)

Mackenna's Gold --> 神龍猛虎闖金關 (sounds heroic)

Sound of Music --> 仙樂飄處處聞 (sounds poetic)

The Longest Day --> 碧血長天 (sounds epic)

The Greatest Show On Earth --> 馬戲千秋 (sounds epic)