Because why not.
Also,quick word of note,the Box test,so you know what I'm baseing this off.

If you lock it in a box,and leave it alone,and it doesn't do anything,that's a Safe Class.
If you Lock it in a box,leave it alone,ans you have no clue what it's gonna do or if it's gonna get out,thats a Euclid.
If you lock it in a box,leave it alone,and it easily gets out,that's a Keter.
If it is the box/lock,that's Thaumiel.
If you can't even get it in the box because it is ending the world,That's Apollyon.
If you could lock it in a box,but choose not to,that's Archon.
If there is no need to lock it in a box because it doesn't have its powers anymore,that's Neutrilized.
If there is no need to lock it in a box anymore because it's dead,that's Terminated.

So,here's a couple villains and where I think they would fall on the rating scale.

For our First Safe Class,Lady WiFi.
The Foundation will probably class her Keter at first,then they find out her weakness of having to use Service/WiFi to use her powers. Then they take that away then boom Safe. She's now just an extra strong person.

Next,a very Suprising Keter,Mr.Pigeon.
Hear me out.
A lot of the SCP's that can control animals like he can have earned their Keter Class. (610,for example)
And he had proven to be quite hard to contain when his pigeons can DENT A METAL DOOR and LIFT THE EIFFEL TOWER,which,may I inform you,weighs 10,100 TONS! This man might be a joke in the show,but not a joke to the Foundation.

Now,a quite surprising Euclid,Glaciator.
Here's why. Now,he is a LSA (Large Scale Agressor) and can Insta Kill,there's one thing that makes him Euclid. His refusal to attack couples. Once the Foundation finds out about this,they would immediately make the containment team all couples,so he wouldn't attack any of them. Thus,earning him Euclid.

Here's a Safe you weren't expecting,Horrificator.
Her powers derive from fear. Knowing the Vets of the Foundation will tell you she isn't scary compared to everything else,rendering her ability to be a LSA out of the picture. Thus,she would be relatively Safe.

Here's a pretty obvious Keter,Mime.
This man can mime anything he can imagine into existence,including stuff that would bust him out of containment. If they try to hand cut him,he mimes a key to get out. They pit him in a blast proof room,he cuts his way out. This man easily gets a Keter.

Here's our actual first Thaumiel,Rogercop.
He could easily be put on MTF Alpha-9 "Last Hope",and he wouldn't even have to be forced if the correct conditions are met. His ability could render any SCP that needs to use their hands to use their ability moot,Like SCP-011,SCP-030,etc. This combined with his (maybe) willingness to he contained,earns him Thaumiel.

I'll do more as I feel like it,but this is it for now.