Who said "My enemies became my teachers."?

This quote is attributed to Arrow.

My enemies became my teachers. - Arrow

"My enemies became my teachers."

Arrow Education

"My name is Oliver Queen. After five years in hell, I have come home with only one goal: to save my city."

"I'm not the man I was."

"You have failed this city."

"I'm a monster."

"Education opens doors."

"Education opens doors to endless possibilities."

"I ain't got the education you got, bub."

"You can't put a price on history."