Hi guys,
I'm a fairly experienced GM, but new to GMing in the 40K universe. I'm having an issue around combat and how lethal it is. Most of my players are fairly well versed in 40K but not all of them. They're used to my GMing style being fairly lenient, I've only killed (i think) one PC in 12+ years of gaming. I'm running this game as much as I can RAW, and I've noticed that most elite enemies can kill a space marine outright in a single hit if they're in the wrong place.
Last week they were going up against a carnifex, and the assault marine decided to charge it's face. I then had to greatly tone down the enemy because it would have quite easily killed him three times over that round.
How do I convey to my players that most enemies in this game have to be approached a particular way or they'll be able to kill you in one hit, without just flat out saying "hey don't just charge this guy or you'll be rolling up a character next round"? Do most GMs have the players take some sort of knowledge checks or research before going up against an enemy like this?