Who said "Show no mercy to your enemies. They would show you none."?

This quote is attributed to Kylo Ren.

Show no mercy to your enemies. They would show you none. - Kylo Ren

"Show no mercy to your enemies. They would show you none."

Kylo Ren War

"I feel it again... the pull to the light."

"Supreme Leader Snoke believes you are the future, but you continue to fail."

"Forgive me. I feel it again, the pull to the light."

"Show me again. The power of the darkness."

"Some battles are worth fighting."

"Sometimes you have to become the monster to stop the monsters."

"Skynet sent me back through time to kill you."

"War teaches us the value of peace."