- “But oh, no, you still think it's neat having Slayer strength. Ooh, big deal! Stronger than humans! Who isn't?”
Strength was the ability to exert physical force, notable when it was greater than what their body would allow. It was a common power among many supernatural beings, though their exact level of strength could vary between beings and races.
- Vampire: Some had described as rising already stronger than when they were humans.
- Turok-Han: A Slayer, with experience against multiple vampires, had significant difficulty against the strength of a Turok-Han when fighting one for the first time.
- Van-Tal: Theorized as the purest form of a vampire's demonic being, Van-Tals didn't include the overall weakness of a vampire's human form.
- Zompire: It was observed that zompires had enhanced strength in comparison to a common vampire.
- Slaypire: They possessed the combined strength of a Slayer and vampire, being notably stronger than before and their vampire counterparts.
- New vampire: Their strength was superior to common vampires by definition; one was able to toss a car aside while an experienced vampire recognized he could not, at least not with the same ease.
- Vengeance demon: Greater than humans, they were able to lift a human and throw opponents flying. Their strength rivaled that of Slayers.
- Mok'tagar demon: Kathy Newman was able to throw a human in the air and overpower the Slayer during a fight.
- M'Fashnik: Could lift and throw humans.
- Fyarl demon: Could break solid wood with ease.
- Kailiff demon: Often employed as muscle-for-hire.
- Vyasa: Could be decapitate humans with ease.
- Lorophage demon: Could overpower multiple humans with ease.
- Baphon: Stronger than vampires.
- Brotherhood of Seven: Could break free from a wooden coffin.
- Nezzla demon: Could throw humans around.
- Burrower demon: Human hosts possessed great strength.
- Ovu Mobani: Possessed humans have great strength.
- Tothric Clan: Could overpower humans with ease.
- Eyghon the Sleepwalker: Possessed humans had great strength.
- Puppet demon: Had great strength relative to their small size, able to overpower humans.
- Granok demon: Could move 2 tons with ease.
- Lei-Ach demon: Could throw humans around.
- Hellions: Capable of decapitating a vampire with their bare hands.
- Spike's crew: Could smash through concrete walls.
Other supernatural beings
- Mummy: Could overpower humans larger than them.
- Troll: Greater than vampires aged 100+ years.
- The Beast: Greater than a Slayer.
- Ugly Man: Greater than a Slayer.
- Slayer: Capable of lifting and throwing human-sized subjects sizable distances, propelling enemies into the air with a single blow, bending solid metal with their bare hands, breaking human bones with ease, and punching into concrete walls to no ill effect.
- Buffy Summers: In addition to being a Slayer strength, she had her strength temporary increased under a enjoining spell, when she was capable of punching through Adam's armored hide; and while empowered by the Twilight prophecy, when she could lift a train with one hand.
- Caleb: Empowered by the First Evil, he was able to shatter solid concrete with his bare hands, snap people's necks with ease, and send an opponent flying dozens of feet with a single blow.
- Marcus Hamilton: Could punch a hole through a man's chest with ease.
- Primal: When possessed, could be almost as strong as a Slayer.
- Severin: After he absorbed large amounts of mystical energy, Severin was strong enough to physically overpower even Illyria.
- April: Could lift and throw humans.
- Bio-mechanical demonoid: Greater than a Slayer.
- Buffybot: Could shatter bricks by punching them.
- Moloch the Corruptor: His robotic body gave him strength greater than a Slayer and he could smash through solid walls with ease.
Higher beings and Old Ones
- Glorificus: Greater than Slayers and vampires. Could level a building by stomping her foot and slaughter hundreds of men in seconds.
- Illyria: Greater than vampires. Still possessed great strength when her powers were diminished. Could shatter a demon's head with a single punch.
There were several means to temporarily increase one's strength considerably.
- Peter Clarner used a special formula to enhance his strength. He was strong enough to break open the library cage door used to house werewolves.
- The drugs the Initiative agents took that were administered by Maggie Walsh enhanced their physical attributes, but not to a supernatural level.
- Equipping the Orbs of Nezzla'Khan would grant a human enough strength to raise the back end an armored car.
- Casting a spell on oneself would grant strength enough to challenge a Slayer..
- Vampires could enhance their strength by drinking special blood.
- A mystical drug could make a Kwaini demon 20 times stronger than its innate strength.
- When Andrew Wells drank from the Asclepian Vial, his ideal self included increased strength described as close to "Golden-Age Superman."