>>44546996First off, it doesn't. At least not in practice because Landorus-Therian can't afford to run Life Orb due to the recoil. Even so it is a mere 0.9% damage difference in favor of Therian if you insist running Life Orb.
252 SpA Life Orb Sheer Force Landorus Earth Power vs. 0 HP / 0 SpD Mew: 230-270 (67.4 - 79.1%)
252 Atk Life Orb Landorus-Therian Earthquake vs. 0 HP / 0 Def Mew: 231-273 (67.7 - 80%)
252 Atk Soft Sand Landorus-Therian Earthquake vs. 0 HP / 0 Def Mew: 213-252 (62.4 - 73.9%)
This obviously extends to their coverage moves which in Therian's case are significantly weaker and less reliable, especially if it's running Soft Sand over Life Orb as it should do. Really, the negation of Life Orb recoil is what makes Sheer Force at its fullest potential one of the best offensive abilities in the game (and also why most physical attackers can't attain this potential, since their moves tend to lack secondary effects). Lando is the closest Pokémon to attain the fullest potential of Sheer Force (and is unsurprisingly permabanned). The Nidos have a much larger movepool but are held back by shit stats, although really without Sheer Force they would be NU at best instead of UU staples with some OU viability.
The prowess of Sheer Force on special attacks (and conversely, its general mediocrity on physical attacks) is so much that you often see some physical Sheer Force Pokémon running mixed sets(I.e. Tauros, Mawile or Rampardos, in lower tiers) despite absurdly low special attacking stats, because the power boost is that much good.
