Always look for subtitles that explicitly mention WEBRip and iTunes in the title.
The most reliable spots for this specific release are OpenSubtitles and Subscene. Simply search for "Deadpool 2016" and filter for the WEBRip versions. Pro-Tip: Multiple Languages subtitle Deadpool.2016.WEBRip.iTunesDeadpool.20...
Most iTunes WEBRip subtitle packs come as a "Mega Pack" including English (SDH), Spanish, French, and more. If you are looking for non-English subs, ensure they are translated from the original theatrical script to keep the humor intact. Always look for subtitles that explicitly mention WEBRip
If your subs are slightly off, you can manually adjust the sync. In VLC, use the 'G' key to delay subtitles or the 'H' key to speed them up. In VLC, use the 'G' key to delay
Subtitle files (.srt) are essentially just text with timestamps. If your video file has an extra studio logo at the beginning or a slightly different frame rate, those timestamps will slowly drift. For a fast-talking character like Deadpool, accuracy is key to catching every fourth-wall break and sarcastic remark. How to Get the Best Results
Finding the Perfect Sync: Deadpool (2016) WEBRip iTunes Subtitles