be the end of one

be the end of (one)

To cause one's ruin, breakdown, downfall, or demise. Often (but not always) used facetiously or lightheartedly. I hate this class, I swear it will be the end of me! My kids are such a handful, sometimes I think they'll be the end of me! If you keep smoking cigarettes, it may well be the end of you.
See also: end, of
Farlex Dictionary of Idioms.

be the end of one

Be one's downfall, as in His heavy drinking may well be the end of him, or That math assignment will be the end of me. This phrase originally alluded to something that would cause someone's death. Today, while it may be used seriously (as in the first example), it more often is used more lightly (as in the second).
See also: end, of, one
The American Heritage® Dictionary of Idioms by Christine Ammer.
See also:
  • be the end of (one)
  • slum it
  • swear down
  • bane of (one's) existence
  • existence
  • the bane of somebody's life/existence
  • the bane of (one's) life
  • I'm so sure
  • I am so sure!
  • if it's the last thing I do