As more relevant feats come out, I will try to add them. However, out of all the respect threads out there, I feel this is the most bang for your buck for feats and info. In this thread you will find feats and details for Buffy, Angel, Spike, Faith, Illyria, and Willow in that order.
Buffy, The Vampire Slayer
Buffy is a young girl who turn into the next Slayer with the death of the past one. Buffy turn out to be very different when she broke the Slayer chain by wanting to live, and then broke the Slayer line altogether. Buffy is known as the greatest warrior on the planet, to all manner of demons and gods. Saving the world several times from certain Armageddon.
Buffy is one of the most skilled characters in fiction. She was born with the innate skill of past Slayers, and their memories. After activating as the Slayer, she was proven to have these memories of fighting in full.
In the famous episode that touch on innate skill, it is stated Slayers on the subconscious level have the memories, and experiences of past slayers. When they "Activate" the skills are natural and present in them to a degree. They cannot recall experiences and such when they try to, but they have it in them. Proven in this episode when a young girl who "activated" had the skill and memories of the Boxtor Rebellion Slayer that Spike had killed, speaking a asian language, and enough skill to decimate Spike. Even though said girl had no training, or was taught any other languages. This is also shown in the canon origin comic of Buffy.
Scan 1-2 shows how Buffy growing up she experience the lives, and deaths of past Slayers just like the little girl Slayer in the episode above. Scan 3 flat out has Buffy explaining she has thee memories of fighting and killing from various Slayers before her. Scan 4 states Buffy's untouched mental prowess as well in the same issues of her past memories.
As stated here when Buffy releases the potential in all Slayers to be full fledged Slayers, this Slayer Gigi is hit with the shared memories of past slayers.
All this comes to a head in the canon season 8 comics, when Buffy faces Fray. Fray had no connection to past Slayers, no memory of them. Buffy overcomes Fray using her memories of every past Slayer's battle. This is stated directly, showing experience triumphs over brute force. Thats three examples of how past lives provide a string innate skill for Slayers, and Buffy more so.
Buffy then honed these skill in a very strict training environment for three years with Giles, aka Ripper, who was one of the top Watchers ever known. Just to drive the point home on Giles training, and Buffy's innate skill, here is a example of Buffy's first training session shown in the first few episodes when Giles attempts to teach Buffy the basics.
With zero training and effort, Buffy effectively uses official weapon maneuvers and styles to beat Giles on her first day of training with the quarter staff. Even though Giles been taught all his life as a kid weapon styles, hand to hand, and magic by the Watchers. Innate skill pulling through. Giles still spent over three years honing Buffy's skills to the best it can be, which shows thanks to Buffy 7 seasons, and 100s of comics. Like Kendra who trained all her life, Buffy was a expert in all weapons (minus gunpowder age one) in a few short years.
We do know in her hand to hand training with Giles, Buffy uses a advance hybrid form Akido and Jujitsu. We also know Buffy spent most of a last school year training with Angel who knows Judo, so its safe to say she learn that as well. This leads to some facts that she is proficient in those three forms that we know about for strict hand to hand.
Kendra, another Slayer that was in her mid teens already was an expert in all weapons (minus guns) and notices differences in weapons. More evidence of Slayer training by Watcher in a few years, and the innate skill that goes with it. However in this scene Kendra who is a Expert in all weapons, showed a misunderstanding of the weapon design that Buffy used, to which Buffy replies she can show her a thing or too.
Giles had even train gone as far as to teach Buffy to fight blind, which Buffy uses several times on invisible, or unseen foes.
First fight against a invisible foe. Hears the very creaking of wood from a single movement. This was before she had any training. Natural talent.
Halfway Season two, second year of training, Giles runs out of ideas of things to train her in. Tries blind fighting, and yet Buffy not only manages to know where Giles is at, but bounce a ball off the wall to tag him. Her first official Blind Fighting exercise.
Buffy was nearly ambushed by three invisible demons, only to hear them sneaking on her. She then manages to fight them all and beat them down.
Buffy again faces off against a Watcher blindfolded taking out him, and another target.
Here Buffy is invisible, as well the mad geniuses Warren, Andrew, and Johnathan. While the mad geniuses of tech and magic could not handle fighting invisible, Buffy was fighting them fine and landing kicks and grabs no problem.
Buffy with her eyes closed catches with her hands a killing thrust by Angel. Need I say more? In short, Buffy is incredibly well train in the lore thanks to Giles, Angel, and her own Slayer past lives.
Unlike most people on this thread who use variety of weapons as plot demands, Buffy is known for one weapon she uses above all.
The Slayer Scythe is a powerful magical weapon, directly link to the Seed itself, which is the source of all magic in the Universe. This weapons is statedas second to Excalibur as a magical weapon, and to be unbreakable It has broken only twice in showing. First time against a fight with Fray by Buffy herself, though being in the far flung future, the Scythe itself is questionable as the original. Then again against the Seed which is the source of all magic that only something as powerful as the Scythe could break. Its so effective as a magical weapon, that even when broken, it can generate energy to rip holes in reality. That is how powerful the weapon is.
Not only is Buffy insanely skilled, but she has incredible accuracy as well.
As seen, Buffy uses Stakes and blades as successful range weapons. Hand throwing them great distance in some of these scans with accuracy to nail the heart of super fast vampires.
With accuracy and ability to use anything as a weapon, nothing is safe.
Buffy as a Slayer is imbued with awesome Super Strength.
Buffy Striking Strength is enough to smash apart thick logs with a blow. Smash through a wall causally. Smash through a brick wall with no effort. Explodes a solid statue with a kick. Punches her hand clear through a giant demon beetles skull.
Buffy is shown strong enough to carry a man up the side of a building with one hand, and throw another roof to roof with one arm. Buffy can also casually lift steel I beam by herself fine. Buffy higher end shows her one time lifting with all her might a large iron gate, something the dozens of slave laborers could not manage themselves. Spike failed to lift the Troll Gods hammer, however Buffy one hands it fine.
Buffy also shows some high ends in strength when she bend rifle barrels in her hands. Able to crush a steel midevil helmet in her hand. Even go as far to bend steel bars of a prison cell with her bare hands.
Buffy also possess speed surpassing even the best of Vampires.
Buffy chases after a speeding bus from roof tops, after being stab in the stomach no less.
Here Buffy steps on a Bear trap in the dark, but then pulls her foot out before it snaps shuts in a slow motion shot. These traps close at speeds faster than you can see, and well over 300 FPS.
Various feats of bullet timing from point blank shots, multiple shots by a high train Watcher, gunfire of a army, rapid fire from Darla, and heavy gunfire from two sides at one time by Watchers.
Pushes Faith out of the way of lightning after it was released at them.
Various showings of afterimages of Buffy moving faster than her surroundings which seem to be standing still even though they are in mid motion.
Vampires are shown time and again to be too fast to be perceived by human eyesight, shown as blurs. They are also stated to have skill where none existed in life, part of the Vampire package. These two things make them pretty hard to fight in terms of speed when comparing the Vamps speed and reaction abilities.
Buffy is shown several times blitzing large groups of these fast and skilled Vampires before they can react.
The Hell God known as Glory is time and again shown as a blur with woosh, or windy sounds for her fast movements.
Here as a combat sped feat is Glory killing a stated 100 men, which was a shown army of knights, in the time it took Buffy to run inside the building, yell at Willow to drop the shield, and run back out. In show time 12 seconds. Glory killed hundreds with a prisoner in tow in 12 seconds, and was gone from the battlefield.
We know that Glory uses this speed in her fights with Buffy, even though it does not look like it, thanks to Buffy Bot. Buffy Bot tried fighting Glory and was soundly defeated, here though states unusual Glory is not moving with her usual blur speed to the robots own super senses. Fact is Glory is well documented super fast in combat speed even though the show budget, and action does not show it for the obvious reasons.
As a Slayer Buffy has incredible blunt force resistance.
Here we see a Slayer (Gigi) tank a Semi Truck. Buffy hit with enough force to break a very large tree in half. Squeezed and smashed into walls by the Old One Malkor. Hit by a Speeding Car to no effect. Smashed into a stone column, knocking the middle piece out. Last scan is a good feat of Buffy and Spike banging each other so hard that the house falls in on them.
Glory can punch down large steel doors with ease, and crater concrete walls with Buffy fine. In their first fight, Buffy was tanking these powerful blows from Glory well enough. At the end of this fight Buffy Grabbed the priest, and jumped out a 3 stroy window, having the priest land on top of her to break his fall. She is relatively fine after all this.
Buffy's energy durability is top notch as well. Shrugging off 12,000 volts taser fine. Tanking a house busting explosion, and set on fire from it with no real damage.
Buffy also has a very effective minor healing factor to heal wound in battle.
States to have a healing factor. Riley is covered in bruises everywhere from a fight, but notices Buffy has no marks on her at all even though she took as much a beating. Buffy states her healing factor, comparing it to Angels. Buffy is shown in a never ending battle of gladiator demons to be healing various wounds from the last fight to keep on fighting. Buffy suffers a critical flu that hospitalizes people for weeks, but she is cured overnight.
Buffy has strong resistance to mind control powers of various foes.
This resistance worked against the likes of Loloth, The Master, and Dracula.
Buffy vs Angel
Some of Buffy's best fights been against Angel himself.
Buffy vs Spike
Collection of her best battles involve facing Spike.
Buffy vs Adam
Adam was a cyborg Frankenstein monster. Possessing super durability, strength, and intelligence that trump Buffy's own.
Buffy vs Amy
Amy is a powerful witch on the same level as Willow roughly. Buffy with her Slayer girlfriend takes down a whole military army with non lethal blows. Then face Amy coming out as the winners.
Buffy vs Alexia
Alexia is the Watchers top field agent. through Magic she is boosted in stats to match Angel. Alexia also packs various gear and magical weapons. When Buffy came to Angel's rescue, she quickly took down Alexia and most of her toys.
Buffy vs Slayers
Buffy casually takes down three other Slayers while holding back.
Buffy vs Gigi
The Slayer Gigi was trained to take Buffy down, but fails in her fight.
Buffy vs Fray
Buffy faces the very skilled and powerful Slayer named Fray. Fray who has dozen comics to her own name had advantages of home turf, purpose, willing to kill, and strength over Buffy's own. Yet Buffy skill and fighting memories allowed her to beat Fray.
Buffy vs Faith
Collection of Buffy's fights with Faith.
Buffy vs Simon and Malkor
Simon was no joke, as she was shown capable as a Slayer to beat down Spikes army, and deal with Spike at the same time. The bugs themselves have super strength to tear down concrete walls, and metal armor. Simon was not a Slayer to take lightly.
At the end of Season 9, Buffy with just her Scythe takes on a large demon army of super stats daemons with varying abilities, and magic users. This is a insane feat as Willow using Dark Magic was hardly making a dent! You know how super powered Willow is? New Avengers Doctor Strange level my man. Buffy was out preforming her on the ground in the thick of it.
Then in the conclusion we see Buffy survive that mess above ground to end up facing this insane dragged out battle under ground vs Simone and a Old One. Simone is a trained Slayer turn feral Vampire. Feral Vampires have greater stats than normal ones, and her being a trained Slayer means skill with more amps to stats! Buffy holds her own for a long time, gets toss to a Old One, a demon as powerful of Glory, and Illyria, and then Buffy survives that beating only to get the best of Simone in this terrible shape. Survives the explosion as well.
Buffy vs Glory
Glory was a powerful hell god with super strength, speed, and invulnerability of a very high degree.
Buffy vs Dark Willow
In this fight Buffy faces Willow who cannot use offensive magic, but does amp herself with Magic to face Buffy.
Buffy vs Caleb
In this battle, Buffy takes on The First Evil's empowered right hand man.
Buffy vs Twilight
How about Buffy surprising and facing twilight? the guy who can out run and puck out of the air bullets, and has strength to crush mountain tops? Buffy is running hard another Slayer, fighting Vamps while out pacing the other train Slayer, and then puts up with his Ambush by Twilight, with no issues, and even speed wise surprises him with a agile counter attack.
Buffy vs The Siphon
This character kills gods for laughs. He is able to absorb the power of anyone with his presence alone, and drains them. He is shown to have enough power at any given time to decimate Illyria herself in a fight.
Here is Buffy against the Siphon who fed off the sum energy and power of over 30 vampires, and Buffy, while she had no shot at winning, still dragged the fight on long enough to force Sev to recharge on Zompires he had in storage. This guy who makes Illyria his bitch, had major issues with Buffy alone.
Buffy vs Giant Vampire
Buffy drops the giant magic enhance vampire.
Buffy vs Pure Demons
Just another great feat of Buffy fighting a soul sucking muck demon to great effect with Spike. A impossible task to carry on, much less harm the demon enough to weaken it where it knew it will lose. All the while avoiding having her soul suck.