>>22952928That's not a safe switch, at all
252 SpA Life Orb Sheer Force Landorus Earth Power vs. 252 HP / 216 SpD Mega Slowbro: 216-255 (54.8 - 64.7%) -- guaranteed 2HKO
For something to switch in safely, it needs to take any possible hit from Landos viable moves, which include Earth Power, Psychic, Sludge Wave, Knock Off, Focus Blast, Rock Slide, HP Ice
And on top of that you need to think, is he Rock Polish 3 Attacks, is he CM with (coverage move), is he mixed for ZardY, is he SR+3 Attacks
It can run a bunch of sets and any of them can completely fuck you over if you give it a free turn
I don't think anything in the game, that's viable in OU, can switch into Landorus-I and force it out, outside of Blissey.
But even then, Blissey can lose to Rock Polish since it can afford to go with a +Spa nature
252+ SpA Life Orb Sheer Force Landorus Focus Blast vs. 4 HP / 252 SpD Blissey: 286-338 (43.8 - 51.8%) -- 71.1% chance to 2HKO after Stealth Rock and Leftovers recovery