adverb, adverb taking the 'to' particle
Indicates that something has changed fully or that a state is absolute. Often used when a situation has transformed completely, or when someone has forgotten or finished something entirely.
彼のことはすっかり忘れていた。
I had completely forgotten about him.
春になって雪がすっかり溶けた。
Spring came and the snow melted completely.
準備はすっかり整いました。
The preparations are completely ready.