Closest things to no weaknesses are HP Dark Weezing/Gengar--they are weak to Ground but they have Levitate, so only Earth Power Kyu-B/EQ Excadrill with Teravolt/Mold Breaker respectively can hit them for SE damage.

ON a more serious note, what are your thoughts on Dark Azumarill? It looks like it could be promising with STAB knock off alongside its already good STAB in Water/Fairy. Being weak to fairy is :/ but fairy is not that prominent in this meta.
Also Steel Sylveon? It looks like a solid wishpasser which hits decently hard compared to clefable.
Edit: Fuck I wasted my 400th post