Sforno on Exodus 12:23/ספורנו על שמות י״ב:כ״ג

1לנגוף, to afflict them with the afflictions G’d will visit on the Egyptian people other than deadly plagues. Whenever the expression נגף is used it refers to afflictions that do not result in death. A well known example of this is found in Exodus 21,22 ונגפו אשה הרה ולא יהיה אסון, “and he pushes a pregnant woman without causing any death, etc.”

2המשחית, the Egyptian people by one of G’d’s other attributes expressing His anger.