not the half of it, phr. — Green’s Dictionary of Slang

not the half of it phr.

a phr. implying that there is much more to come, to be recounted.

1932		(con. 1919) Dos Passos Nineteen Nineteen in USA (1966) 652: And that’s not the half of it.
1997		P. Theroux Kowloon Tong 208: There won’t be any money. And that’s not the half of it.
1999		K. Vonnegut Bagombo Snuff Box 4: That isn’t the half of it.