(I don't know where else to put this so sorry if this is in the wrong place)
Okay before you say anything, I already have my neighbourhood/downloads/etc backed up so if there is actually a way to do this and my game breaks when I try it won't be a total loss.

Anyways, the main "issue" I'm having is that the Grim Reaper in my game has two spaces at the end of his name making it look a bit off (For reference note the large gap between "Grim Reaper" and "(NPC)"). I use clean templates and I know that if you use default, maxis templates then Malcolm Landgraab has a similar issue but the difference is that since Grim is considered an "uneditable sim" in SimPE I can't fix it as easily as I can with Malcolm so I was wondering if there was anyway to fix this?

As I said, since I use clean templates the Nervous Subject in Strangetown is related to Grim on the family tree and it kind of bothers me how whenever I look at Grim's name on Nervous' family tree (or if a sim dies ) there'll always be two spaces at the end of his name.

I suppose you could remove the spaces in SimPe, in his Sim Description, but I personally wouldn't recommend it because of the obvious reason: universal NPCs shouldn't be modified because it will probably break their behavior and thus, the game. But, in the unpatched version of the base game, Strangetown Grim Reaper was considered female, before they changed it with a patch, which I would consider modifying his data. If you really want to, you can change the name, but make sure to have a backup of your objects.package as well, just in case something goes wrong. I would consider having an actual Sim that looks like Grim Reaper to be a safest option, at least for the family tree purposes.

You simply can't fix it, Grim Reaper does not have (NPC) as part of his(her) name. That is something SimPE 'tacks on' to all NPC Unique sims when you view the neighbourhood.

We don't know, is the thing. It's only a text string so it might be all right; but any unintended consequences will affect your game files, not just your neighborhood. No one here's going to advise you to do it. If you try, it will be at your own risk.
SimPE's probably the only place you can get at that text string to edit it, because Grim's data is bundled into the base game objects package, and SimPE is the only way we have of editing text strings in package files.
Personally, I would treat this as an opportunity to train yourself out of perfectionism, a flaw which is fatal to living your life to the fullest in this imperfect world. You won't see those spaces very often and when you do, you can learn to ignore it.
But if you do the edit, pay attention and report back periodically on the state of your game, so we can learn from the risk you take.

If you do it, and after you play for a while, check if your objects.package has been modified. If it gets modified, then you probably shouldn't have done it.

The objects package will get modified if he does it. That's where the change is made. It cannot be done without changing the objects package.
Looking for changes in your objects package is what you're told to do if you're afraid your game files are corrupted; and making the objects package read only is what you're told to do in order to prevent accidental changes and corruption of the game files, because that's where it's most likely to happen.

The first post they say they don't care if their game breaks, so... *shrug* Go right ahead and let us know what happens.

I'm not sure why some free space at the end of his name is an issue in the first place though. You must see Grim a lot for it to bug you.

Nobody can tell you how to do it because we have not tried it since we do care if our game breaks. I've played for 15 years and never even noticed it.

There is no blank spaces at the end of the name, the name is blank in English but in US English which it'll default to Grim Reaper is the first name and the surname is blank so SimPE adds a blank space between the first and second (which doesn't exist) names and another blank before the (NPC). Overriding the name, catalogue description is quite safe to do but it won't fix a problem that does not exist.

I only see one space between Grim and Reaper.

There is only one space between Grim and Reaper, it's all one name. Like SimPE the game may add a space to the end in anticipation of a surname but there isn't a space in the catalogue description to remove.
In my game (A&N) her first name is Grim and Reaper is her surname in both English and US English because I did think that looks better. She has a FM D36 bodyshape and her main role is to make deliveries to heaven and hell lots.

if I recall correctly, name changing through Sim Description resources can only be done to characters that have a file in the neighborhood's Character folder. all universal characters do not.

creating a replacement through SimPE's Object Workshop might be safest way to change any universal's name. Character Description resource. put the finished file in the Downloads folder.

But Reaper is the last word, so you can't see any spaces after it.

There is a space, but I think the game considers it to be his last name because Grim Reaper (both words) is his first name, and since he has no actual last name the game just displays a space. I think that in base game this is not an issue since the tooltip (when you hover over a Sim) displays just the first name anyway, so Maxis never altered it later when the game started displaying full names.

There is a space after Reaper, but that doesn't bother me. So you want (NPC) to be bang up against Reaper? Grim Reaper(NPC)
We all get bothered by different things I guess, I would not even notice his label.

In the screenshot I don't see the (NPC). Doesn't that only show in SimPE?

You don't? The attached image reads 'Grim Reaper (NPC)'

Yes, it is something SimPE adds to all of the unique NPCs in neighbourhood view.

Not the in SimPE image. The in game image.

You can, apparently. I can't. From my perspective, the second thing seems more likely. But I don't notice a lot of things that drive other people crazy.

I can see the spaces in SimPE. I just never bother looking at the Grim Reaper in SimPE. In game you can't see it. Not that I see the Grim Reaper much in game either. XD