twenty-twenty hindsight, with

twenty-twenty hindsight

The ability to determine how some mistake or failure in the past could have been avoided. Often used ironically or sarcastically; sometimes stylized as "20/20 hindsight." I can see now that having my brother as my legal counsel was unwise, but I guess twenty-twenty hindsight isn't much use right now. A: "I can't believe I was ever interested in such a self-absorbed jerk." B: "Don't beat yourself about it. We all have 20/20 hindsight."
See also: hindsight
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

twenty-twenty hindsight

Knowledge after the fact, as in With twenty-twenty hindsight, I wouldn't have bought these tickets. This idiom uses twenty-twenty in the optometrist's sense, that is, "indicating normal vision," and hindsight in the sense of "looking back" or "reconsidering." [First half of 1900s]
See also: hindsight
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

twenty-twenty hindsight

and 20/20 hindsight
n. an ability to figure out what one should have done after it is too late to do it. Everybody has twenty-twenty hindsight!
See also: hindsight
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.

twenty-twenty hindsight, with

With complete after-the-fact knowledge. This expression, usually preceding a statement like “I would have done or said such-and-such,” uses the optometrist’s term for perfectly normal vision. The idea that hindsight, with its superior knowledge, is better than foresight has been stated since at least the nineteenth century. “If a man had half as much foresight as he had hindsight, he’d be a lot better off,” wrote Robert J. Burdette (Hawk-eyes, 1879). The Hollywood screenwriter Billy Wilder is quoted as having said, “Hindsight is always twenty-twenty.”
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer
See also: