Using moves such as Sheer Cold or Destiny Bond do not count.
There's no Pokémon who can OHKO everything.
It would make competitive Pokémon too unfair. Plus there is sturdy Pokémon, mimikyu, focus sash, to a lesser extent focus band,
Pokémon with lots of defence like tangrowth, big special defense like chansey etc.
Few Pokémon with abilities like teravolt and moves like sunsteel strike ignore abilities, but can't take on focus sash and big defenses.
Thus in conclusion, it would be too unfair so such Pokémon don't exist yet.
Hope I helped!