TORTUROUSLY

agonizingly, excruciatingly, torturously

(adverb) in a very painful manner; “the progress was agonizingly slow”

Source: WordNet® 3.1

Etymology

Adverb

torturously (not comparable)

In a torturous fashion, or as if in torture

Source: Wiktionary

TORTUROUS

Tor"tur*ous, a.

Definition: Involving, or pertaining to, torture. [R.] "The torturous crucifixion." I. Disraeli.

Source: Webster’s Unabridged Dictionary 1913 Edition