as sin

Generalization of previous similes, e.g. evil as sin, common as sin, imputable as sin.

as sin

1. (postpositive) To a great extent or degree; very.
   • 1864, O. E. [Oliver Everett] Durivage, The Stage-Struck Yankee:

     CAPTAIN: I understand, and I'll patronize you. I'll take every ticket, and pay you cash, and Jedidah shall come and see the beautiful rival. / JEDIDAH: Beautiful! She's as homely as sin.

   • 1945, Taylor Caldwell, Wide House:

     As for Janie, she stood there, petrified, and now her face had become as ugly as sin, and as vicious, and as malevolent.

   • 2015, John C. Wright, The Architect of Aeons, first edition, New York:

     The clouds covered a liquid surface black as sin.

   There is no way you'll lift it yourself, it's heavy as sin.

• ASINs, Sains, sains, sasin