TANTALISING

"Tantalizing" means tempting, teasing, or arousing desire without fulfillment.

Now, let’s analyze the options:

A) Toiling → Means working hard; not opposite to "tantalizing."

B) Seance → A spiritual meeting; unrelated.

C) Repulsive → Means disgusting, unattractive, or revolting, which is the opposite of something that is tempting or enticing.

D) Seamy → Means unpleasant or sordid, but not exactly opposite to "tantalizing."

Thus, the best antonym is "Repulsive."