What is 輸打贏要? (Cantonese expression)
The Cantonese expression 輸打贏要 came from Mahjong lingo
'Play Mahjong' in Cantonese is &quot;打麻雀(麻将)'

輸 means 'lose'

輸打 means 'continue to play when losing' (so when the game ends, he will have the chance to promise a gambling debt instead of paying the cash)

贏 means 'win'

贏要 means 'demand payment after every winning hand' (so when the game ends, he will get the cash and not a promise of repaying a gambling debt)


As a former Mahjong player, 輸打贏要 to me refers to the behavior of refusing to pay up after every losing hand when he was losing, insist on continuing to play, until he was winning, and then comes the 贏要 part -- Now he is demanding payment right after every hand.
In short -- Refuse to end the game when losing; eager to end the game when winning'; pick and choose the rules to obey when it benefits you
It is similar to the English expression 'Keep moving the goalposts';