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).
Words nearby be the end of one
be on to,
be oneself,
be prepared,
be that as it may,
be the death of,
be the end of one,
be the making of,
be-,
be-all and end-all,
be-all and end-all, the,
bea