Dark Souls – Is Knight Lautrec of Carim an Evil NPC?

You can kill NPCs in Dark Souls, just as you did in Demon's Souls. Some people kill Lautrec early on, for example, to obtain his very useful ring. If you ever accidentally harm a NPC, they will be hostile towards you, but you can "absolve" your sins at the NPC "Oswald of Carim" in the Church after the Bell Gargoyle fight to make them unhostile. The cost is Soul Level x 2000. Some covenants will also become hostile if you dishonorably leave them (abandon covenant without use of Oswald, betray their rules, etc.), which is also something that can be absolved at this NPC.

Unless you kill Oswald, you can always resort to this method to make the NPC's like you again (note that this won't revive them however if you killed them).

You might miss out on some story/sub-plots, but you should still be able to complete the game having killed all the NPC's that you are allowed to kill. It is hard to say for certain what the impact on the game will be as there are so many NPC's in the game with different functions.

I'm really not so sure what you're talking about either...are you referring to the Dark Knights?

If so, these guys are pretty powerful at the point of the game you're at - they're placed in locations that you can easily avoid, so for the moment you can run past them and come back to fight once you're stronger.

They also don't respawn so you don't need to worry about having to fight them again after you take them down once.