Clytemnestra is addressing her daughter Iphigenia who is at the time of speaking still in good health and among the living. Guy Cooper states that the use of the aorist with verbs of killing is idiomatic (tragedy) even when the killing never takes place. His examples involve κτείνω which in this context is a participle. Ἀπώλεσέν however is a aorist indicative referring to a future event at the time of speaking. Some would perhaps suggest that Clytemnestra chooses to present the killing of Iphigenia as an accomplished fact when it has not yet transpired.Iphigenia at Aulis 1177-1178
Ἀπώλεσέν σ', ὦ τέκνον, ὁ φυτεύσας πατήρ,
αὐτὸς κτανών, οὐκ ἄλλος οὐδ' ἄλληι χερί,
Euripides Trag., Iphigenia Aulidensis
Ed. Diggle, J. Oxford: Clarendon Press, 1994.
“Daughter, the father who begot you has destroyed you, killing you himself! It is he and no one else nor by any other’s hand,”
D. Kovacs 2002, Harvard UP.
According to David Kovacs, the text under consideration was not written by Euripides the elder or the younger. He brackets most of Clytemnestra’s speech as an addition by the fourth century reviser.
In another place Cooper shows two examples from Euripides of ἀπόλλυμι but he claims that this only happens in a conditional context which doesn’t apply to Iphigenia at Aulis 1177-1178. Carl Conrad addressed Cooper’s two examples from Euripides in 2006.
http://www.ibiblio.org/bgreek/lists.ibi ... 40142.html
 Greek Syntax, vol 3, p2377, 2:53.6.0
 Attic Greek Syntax, vol 1, 126.96.36.199.B