At the very least, as a matter of fact, as in I know only too well that I can't win the lottery. This usage was first recorded in 1817.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
How to use only too in a sentence
The thought that he was addressing his heir-presumptive—now heir-only-too-apparent—gave him pause.Zuleika Dobson | Max Beerbohm