"The Apple" and "Obsession" are particularly hard on Security personnel. What is it, at least 7 or more in total over the two episodes?
Nomad kills two(?) in "The Changeling." Two die by accident in "And The Children Shall Lead." The rest are killed individually here and there. We have no idea if any Security personnel were among the 9 casualties mentioned by Spock in WNMHGB. We also don't know if any Security personnel died from their injuries after the alien with its influence departs in "Day Of The Dove."