You all need to remember that not its viability or likeability is in question, but rather its prowess as an ekiller check.
In my opinion Clefable is a viable pokemon in the tier, but besides that, it is able to check Ekiller.
Why shouldn't it be listed as such when the latter is a fact?
Just because the majority doesn't like to include it in their build, or question its viability?
I don't think so, and would have to agree with Transcendent God Champion.
Even though Clefable might not be as solid of a pokemon to use as other (shady) ekiller checks, its ability to do the former cannot be denied.
When I talk about shady ekiller checks, I'm talking about offensive ghost types for the most part.
Pokemon like Lunala and Mega Gengar, who rely on hitting a Focus Blast to kill it, and would either straight up die, or be killed in 2 if Focus Blast misses (I get that they're offensive checks and all, but still).
By Dominatio's logic of saying it can't switch into an Adamant Ekiller (which btw isn't true, it can), for example Primal Kyogre wouldn't be a Ho-oh check, as even a defensive variant can't switch into any viable variant of Ho-oh.
252+ Atk Life Orb Arceus Extreme Speed vs. 248 HP / 248+ Def Clefable: 156-185 (39.6 - 47%) -- guaranteed 3HKO after Leftovers recovery
252+ Atk Arceus Extreme Speed vs. 248 HP / 248+ Def Clefable: 120-142 (30.5 - 36.1%) -- guaranteed 4HKO after Leftovers recovery
196+ Atk Life Orb Ho-Oh Brave Bird vs. 248 HP / 248+ Def Kyogre: 208-247 (51.6 - 61.2%) -- guaranteed 2HKO
252+ Atk Choice Band Ho-Oh Brave Bird vs. 248 HP / 248+ Def Kyogre: 250-295 (62 - 73.2%) -- guaranteed 2HKO
I'm not trying to deny their capability to check, but rather trying to prove that Clefable should be listed as an ekiller one.
In my opinion, it is a noteworthy enough one to the point where I think it should be listed.