The only good Keter SCP in my eyes is 076, who has a good story. He's a Sumerian heroic warrior, a demigod of sorts, but after killing the SCP personnel a thousand times he gets bored and works with them. He has a personality, a code of morals, he's fleshed out. There are multiple tie-ins and a lot to think about with him.
The thing is most Keters are dumb and work on a gimmick -- mostly DON'T EXPOSE TO LIGHTS/MIRRORS/DARK/OTHER PEOPLE/THE OUTSIDE WORLD/etcetc OR ELSE WE ALL DIE. What the fuck, people, you failed Creative Writing for a reason, don't write SCPs.