to say the least
Not to exaggerate, as in When the ring turned up in the lost and found, she was delighted, to say the least. This idiom was first recorded in 1809.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.