Snakeman.
Perhaps simple, but I celebrate each victory like that.
Luckily none of Chryssalid killed anyone. And the blaster launcher was not used either.
Sadly, a Colonel died in a really funny/sad way: I was guarding the east-north window of the command centre, and that area was supposed to be cleaned... but nope, shot through the window.
It's early game and we're in alloys only, so RIP.