Well, I figure being hit straight in the chest with a blasting curse or Dolohov's Purple fire wouldn't be so good for your life span. There must be dozendozens of lethal curses we never heard about in the canon. No need for sectum sempraA simplesempra; a simple Diffindo at the throat would be deadly:
"D-diffindo, " she said, pointing her wand at Ron, who roared in pain as she slashed open the knee of his jeans, leaving a deep cut.
A spell violent enough could crush your skull, stop or stop your hearheart. AK is simply the fastest and most efficient way to kill with magic. The as As fanfiction writers like to call it, there must be the whole branch of 'Battle"Battle Transfiguration" spells to conjure knives, arrows, and suchsuchlike.