Who said "Mercy is a luxury we cannot afford."?

This quote is attributed to Lannister.

Mercy is a luxury we cannot afford. - Lannister

"Mercy is a luxury we cannot afford."

Lannister Justice

"A Lannister always pays his debts."

"I am the god of tits and wine."

"You are an awful man."

"I drink and I know things."

"Justice must always prevail."

"You think I'm just some animal?"

"Fighting for what's right never gets easier."

"Justice is worth fighting for."