If you factor in both Sheer Force, and Life Orb, you abe basically firing off a 154 BP Psychic attack from a non-STAB base 115 special attack (if I am doing my mat correctly at 90 BP x .30 x .30 = 154, where the .30 each are equal to the Sheer Force boost, and the Life Orb boost.
More than enough to KO Breloom. No hazards required...
Lando Sheer Force + Life Orb versus 4 / 0 / 0 Breloom: Damage: 460 - 542 of 262 HP 175% - 206%
Could almost KO Breloom twice with one hit.
EDIT
I don't personally suggest HP Flying, but if anybody is interested in the damage calc...
Lando Sheer Force + Life Orb versus 4 / 0 / 0 Celebi: Damage: 272 - 320 of 342 HP 79% - 93%
EDIT2
All of the questioned OHKO's / 2HKO's.....
More than enough to KO Breloom. No hazards required...
Lando Sheer Force + Life Orb versus 4 / 0 / 0 Breloom: Damage: 460 - 542 of 262 HP 175% - 206%
Could almost KO Breloom twice with one hit.
EDIT
I don't personally suggest HP Flying, but if anybody is interested in the damage calc...
Lando Sheer Force + Life Orb versus 4 / 0 / 0 Celebi: Damage: 272 - 320 of 342 HP 79% - 93%
EDIT2
All of the questioned OHKO's / 2HKO's.....
252SpAtk Life Orb Sheer Force Landorus (Neutral) Psychic vs 4HP/0SpDef Gliscor (Neutral): 65% - 77% (192 - 227 HP). Guaranteed 2HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Psychic vs 4HP/0SpDef Multiscale Dragonite (Neutral): 23% - 27% (76 - 90 HP). Guaranteed 5HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Psychic vs 4HP/0SpDef Dragonite (Neutral): 47% - 55% (153 - 180 HP). Guaranteed 3HKO. 17% chance to 2HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Psychic vs 4HP/0SpDef Salamence (Neutral): 55% - 64% (183 - 215 HP). Guaranteed 2HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Hidden Power (Ice) vs 4HP/0SpDef Multiscale Dragonite (Neutral): 55% - 65% (180 - 212 HP). Guaranteed 2HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Hidden Power (Ice) vs 4HP/0SpDef Dragonite (Neutral): 112% - 132% (364 - 428 HP). Guaranteed OHKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Hidden Power (Ice) vs 4HP/0SpDef Salamence (Neutral): 132% - 156% (440 - 520 HP). Guaranteed OHKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Earth Power vs 4HP/0SpDef Volcarona (Neutral): 70% - 82% (219 - 258 HP). Guaranteed 2HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Earth Power vs 240HP/0SpDef Volcarona (Neutral): 59% - 69% (219 - 258 HP). Guaranteed 2HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Earth Power vs 4HP/0SpDef Venusaur (Neutral): 75% - 89% (229 - 270 HP). Guaranteed 2HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Hidden Power (Ice) vs 4HP/0SpDef Venusaur (Neutral): 60% - 70% (182 - 214 HP). Guaranteed 2HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Psychic vs 4HP/0SpDef Venusaur (Neutral): 101% - 119% (306 - 360 HP). Guaranteed OHKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Psychic vs 4HP/0SpDef Multiscale Dragonite (Neutral): 23% - 27% (76 - 90 HP). Guaranteed 5HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Psychic vs 4HP/0SpDef Dragonite (Neutral): 47% - 55% (153 - 180 HP). Guaranteed 3HKO. 17% chance to 2HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Psychic vs 4HP/0SpDef Salamence (Neutral): 55% - 64% (183 - 215 HP). Guaranteed 2HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Hidden Power (Ice) vs 4HP/0SpDef Multiscale Dragonite (Neutral): 55% - 65% (180 - 212 HP). Guaranteed 2HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Hidden Power (Ice) vs 4HP/0SpDef Dragonite (Neutral): 112% - 132% (364 - 428 HP). Guaranteed OHKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Hidden Power (Ice) vs 4HP/0SpDef Salamence (Neutral): 132% - 156% (440 - 520 HP). Guaranteed OHKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Earth Power vs 4HP/0SpDef Volcarona (Neutral): 70% - 82% (219 - 258 HP). Guaranteed 2HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Earth Power vs 240HP/0SpDef Volcarona (Neutral): 59% - 69% (219 - 258 HP). Guaranteed 2HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Earth Power vs 4HP/0SpDef Venusaur (Neutral): 75% - 89% (229 - 270 HP). Guaranteed 2HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Hidden Power (Ice) vs 4HP/0SpDef Venusaur (Neutral): 60% - 70% (182 - 214 HP). Guaranteed 2HKO.
252SpAtk Life Orb Sheer Force Landorus (Neutral) Psychic vs 4HP/0SpDef Venusaur (Neutral): 101% - 119% (306 - 360 HP). Guaranteed OHKO.