tn The verb is the Qal perfect שָׁלַחְתִּי (shalakhti), but a past tense, or completed action translation does not fit the context at all. Gesenius lists this reference as an example of the use of the perfect to express actions and facts, whose accomplishment is to be represented not as actual but only as possible. He offers this for Exod 9:15: “I had almost put forth” (GKC 313 §106.p). Also possible is “I should have stretched out my hand.” Others read the potential nuance instead, and render it as “I could have …” as in the present translation.
tn The verb כָּחַד (kakhad) means “to hide, efface,” and in the Niphal it has the idea of “be effaced, ruined, destroyed.” Here it will carry the nuance of the result of the preceding verbs: “I could have stretched out my hand … and struck you … and (as a result) you would have been destroyed.”