Expletives used informally as intensifiers:
— I'll be damned (or blessed or darned or goddamned) if I'll do any such thing.
— He's a damn (or goddam or goddamned) fool.

synonyms: blame, blamed, blasted, blessed, damn, damned, darned, deuced, goddam, goddamn, infernal ... show more.

Extremely.

synonyms: goddam, goddamn.