Ho-oh is your man. It always finds a spot on my teams.
4 SpA Spooky Plate Arceus-Ghost Judgment (Ghost) vs. 248 HP / 84 SpD Ho-Oh: 99-117 (23.85 - 28.19%) -- 22.66% chance to 2HKO after Stealth Rock
It can usually switch in even with SR up. It is tricky, I'll admit, but Ho-oh usually makes it work. You just need sun and countermeasures for entry hazards and it will usually work out.
However, Darkrai works too and a specially defensive Skarmory is not 2HKOed by +1 Focus Blast with no rocks up, and works great against the mono-attacker. Specially defensive Jirachi can toxic it and wish/protect stall.