Ilbranteloth
Explorer
It's automatically evil because in the D&D cosmology there is an actual 'good' and 'evil' dichotomy. Certain acts are always evil.
When you start to dissect it, it can get a bit messy. Killing an orc? Good. Pretty much based on the concept of them being a 'monster' along with a nod to Tolkien in that they are a corrupt race that can't be anything but evil. Killing a helpless orc? Generally considered OK as well.
Killing with the intent to raise? Generally speaking the cosmos doesn't take into account intent. It's a black and white thing, much like the light and dark side in Star Wars. Anger, jealousy, hatred, all are paths to the dark side. Whether you continue to follow that path is a different question.
Obviously, in the game world itself a given culture will have very different ideas. In your home campaign you're welcome to do what you want.
But part of what I love about the game is it gives you the opportunity to work through things like this in game. A mercy killing is (and should be) a hard decision to make. In my view, I don't think whether the God will deny the character (paladin or cleric) should even enter into the discussion. That's a metagame discussion, even though there could be in-game repercussions. Nor do I think the DM should weigh in regarding it. The characters should work through the problem and their own point of view. Is turning back an option? Can they abandon their quest and go for help? Can one of them stay and nurse the companion while the other looks for help?
While it's the characters that have to make this decision, it's the players that have to do it for them. Think about your own perspective. If the character is in a coma with no ability to eat or drink, and death is assured in a short time (a few days probably), what do you do? Do you stay with them, comfort them as you can, and provide a proper and sacred death and burial? Or do you kill them and then give them a proper burial? The lifeboat dilemma, Of Mice and Men and other scenarios do make a case for a mercy killing. But not without a personal cost. These are very difficult decisions, which is why these ethics puzzles exist. The concept of actually killing somebody is so against our nature that when placed in that situation it's not only an extremely difficult decision to make, but it often changes the survivor's life, and not usually in a good way.
These are the opportunities to really role-play and delve into the characters. It's what makes TTRPG unique. In my campaign this would probably take up a couple of hours of time, if not an entire session while they agonized over the decision. I'd just be a spectator.
As a DM, from my perspective, I think the cleric and paladin are safe in regards to losing their powers. Falling out of grace with your Deity is a path, much like the dark side. They would definitely ask for atonement, and there's a good chance that the event would haunt them for some time, particularly if it was a friend. And this would be something I would consider along with other and future actions, and there might be repercussions based on that.
Killing and raising is something that I consider just as bad. While the spells exist in the world, how many of the characters have actually seen or experienced being raised? Very, very few characters in my campaign have ever been raised from the dead. Revivify, sure. Raise dead or resurrection? Extremely rare. But then so are 9th level or higher characters in my campaign. Sure, the Forgotten Realms has a lot of them overall, but they aren't in every town, and certainly not there to help every random adventurer that comes looking for help. The temples in a large city might have the capability.
If your campaign is a revolving door of death, you might feel differently. But these are still people with a soul, and cheating death is like cheating your God as well. It's showing a disregard for the sanctity of life. And if it were me, I'd be pretty concerned that there might be consequences later on, like in the afterlife.
