قَامَ الَّذِي ضَرَبْتُ.
Translation: The person I struck stood up.
قَامَ is the main verb; «الَّذِي» is its subject.
ضَرَبْتُ is the relative clause: «تُ» is its subject, and the object ʿāʾid is omitted, underlying «ضَرَبْتُهُ».
Deleting the object does not delete the verb or subject of the ṣilah.