I'm bored right now so I thought I'd do a threat level analysis of every New Who story.
Threat Level:
None - There is no threat to anyone in this episode whatsoever (I don't think anything falls in to this level)
Personal - The episode's major threat is to the Doctor and supporting cast for the episode.
Local - Threat is to the immediate area around which the episode takes place.
National - Threat is to an area the size of a country (most likely to be U.K.)
Global - Threat is to an entire planet.
Species - Threat of the episode is to alter an entire species for the worse.
Universal - The threat applies to the entirety of space and/or time.
Any threat with a * after means I'm not totally sure if I have it right, a ? means I have no idea if my choice is correct.
Series OneSpoilerRose - Global, Nestene Consciousness wants to take over the world for food
The End of the World - Personal, Cassandra tries to hold Platform One hostage/kill everyone on board
The Unquiet Dead - Global, Gelth want a new planet
Aliens of London/World War Three - Global, Slitheen want to cause nuclear war so they can easily sell the minerals (I think)
Dalek - National*, the episode centres around trying to stop the Dalek escaping. Could be bumped up to global depending on how dangerous one Dalek is.
The Long Game - Species, the Mighty Jagrafess of the Holy Hadrojassic Maxarodenfoe was using the media to repress humanity's progress.
Father's Day - Local*, Reapers consume everything in sight. I'm making a guess here that the Reapers will stop at some point here.
The Empty Child/Doctor Dances - Species, Zombie-like plague that would have eventually changed the entire human race.
Boom Town - Global, Nuclear plant that threatens to open the rift and blow up the earth.
Bad Wolf/Parting of Ways - Global/Species*, Daleks threaten to invade Earth, turning a large number of humans in to Daleks(most likely). Could turn daleks in to threat to entire universe.
Series 2SpoilerThe Christmas Invasion - Species, Sycorax want to turn humans in to slave race
New Earth - Local, Zombie plague in hospital
Tooth and Nail - Personal?, Werewolf trying to kill people? I've only really half seen this episode so am unsure as to the plot.
School Reunion - Universal, The Krillitane are trying to solve something that would give them god like powers
The Girl in the Fireplace - Personal, Clockwork Robots are out for Madame de Pompadour's brain
Rise of the Cybermen/Age of Steel - Species, Cybermen want to convert the planet
The Idiot's Lantern - Local*, The wire is trying to eat everyone's mind, she could only reach people in the area Magpie was giving tellys to right?
The Impossible Planet/The Satan Pit - Universal*, The "Devil" getting out of its prison is surely bad thing for the entire universe right?
Love & Monsters - Personal*, Blue Peter monster contest winner wants to absorb the doctor. Did it have any further plans?
Fear Her - Universal, it's so bad it's a threat to the entire universe.
Army of Ghosts/Doomsday - Species/Universal - Cybermen get bored of own universe decide to have a crack at the main one & Cult of Skaro come out of hiding to campaign for shorter prison sentences for war convicts
Series 3SpoilerThe Runaway Bride - Global*, Racnoss would consume all life on earth if awakened, awakened may be universal threat?
Smith and Jones - Local, Judoon puts a hospital at risk to apprehend one criminal
The Shakespeare Code - Global???, What were the Carrionites' plans once released?
Gridlock - Local/National*, The people on the motorway will die eventually because no one can leave. threat depends on number of motorist
Daleks in Manhattan/Evolution of the Daleks - Species/Universal*, Daleks want to create Human-Dalek army, a Dalek army is a universal threat?
The Lazarus Experiment - Local, Lazarus was a threat to the local populace but would likely have been easily taken down
42 - Personal, Damaged starship going to fall in to sun. could be global if you take the stars side in this episode.
Human Nature/Family of Blood - Local*, Family of blood was a threat to the village and school. What did they plan to do with the Doctor's body if they got it?
Blink - Personal, Angel's only seem to be a threat to the cast, don't seem to want anything but to feed off the Tardis
Utopia/The Sound of Drums/Last of the Time Lords - Universal, The Master threatens to start war with/destroy the entire universe
Series 4
SpoilerVoyage of the Damned - National, Starship Titanic is about to crash in to the earth causing a nuclear explosion in London
Partners in Crime - Local, Diet pills were only given to London population.
The Fires of Pompeii - Species, Pyroviles are trying to convert humans into Pyroviles.
Planet of the Ooooood - Species or Local, local threat to the facility from ood, species threat to the Ood as high up offical suit dude plans on destroying the hive brain thingy.
The Sontaran Stratagem/The Poison Sky - Global, Sontaran's plan to gas the earth then use if as a breeding ground
The Doctor's Daughter - Personal/Local?, Not really sure at all here, input wanted
The Unicorn and the Wasp - Personal, The wasp was a threat to the inhabitants, staff, and guests of the manor
Silence in the Library/Forest of the Dead - Personal*, The Vashta Nerada only act according to their instincts when meat enters their territory, they have no plans to spread beyond the library. Was an Ex-global threat however as they were going to kill the whole library when they first awoke
Midnight - Personal, The presence appeared to only be a threat to the people on the ship. We don't know what it would have done once it had returned to civilization however.
Turn Left - Universal, The Trickster's plot would have ended with the Doctor not stopping Davros's reality bomb
The Stolen Earth/Journey's End - Universal, Reality Bomb. duh.
SpecialsSpoilerThe Next Doctor - Species, Cybermen, conquer earth, convert humans.
The Planet of the Dead - Global, the alien hive was going to warp to earth and try to eat it all
The Waters of Mars - Global*, Water virus wants to get to Earth and erm go for a swim?
The End of Time - Universal, Time Lords want to end time
Series 5
SpoilerThe Eleventh Hour - Global, The Atraxi want to burn Earth if Prisoner Zero doesn't surrender itself
The Beast Below - National* - A bunch of shadowey dudes are kidnapping children to help them with the star whale. Also torturing the star whale.
Victory of The Daleks - Global/Universal, Bracewell's heart power plant bomb thingy would destroy Earth. Beginnings of a new Dalek Empire.
The Time of the Angels/Flesh and Stone - Universal?, An army of angels fed from a crack in time couldn't be good, and their plan was to feed on the universe right?
The Vampires of Venice - Local, The vampire fish are trying to sink Venice to create a new home for themselves.
Amy's Choice - None, it was all dreams, they were never in danger.
The Hungry Earth/Cold Blood - Personal*, Silurians are trying to stop the mining project to stop the destruction of their home, did't have plans beyond that I think.
Vincent and the Doctor - Local, The Krafayis was a threat to the populace of the town.
The Lodger - Local, The necro-Tardis was killing people who passed the house so didn't have a large area of influence.
The Pandora Opens/The Big Bang - Universal, all of time never existed.
Series 6
Spoiler
A Christmas Carol - Local, 4000 people on space liner about to crash
The Impossible Astronaut/Day of the Moon - Species?/Personal? - The Silence are controlling humanity so that they can use the space tech to make a suit to make River kill the Doctor?
The Curse of the Black Spot - Personal, The reflection dimension ship is only able to get people who are becalmed in that area.
The Doctor's Wife - Personal/Mild universal?, House is obviously a threat to our main cast, but I don't know what he planned to do once in our universe
The Rebel Flesh/The Almost People - Personal/National?, Ganger versions trying to kill reals (and vice versa), Jenny ganger may have wanted to start a ganger rebellion if she escaped?
A Good Man Goes to War - Personal, The Doctor's army tries to save Amy and her baby (having an army may make this a local threat?)
Let's Kill Hitler - Personal, River Song's poisoning of the Doctor, and the Teselecta's attempted execution of River
Night Terrors - Local, George's scared telepathy was transporting the entire block of flats in to his cupboard.
The Girl Who Waited - Personal, Hand Robots trying to "sanitise" our crew
God Complex - Personal, The beast is trapped in its prison and only a threat to people that get summoned there.
Closing time - Local/Species, Cybermen kidnapping shop assistants, stealing power from the shop so that they can convert the human race.
Wedding of River Song- Universal, Time has collapsed in on itself and is all happening at once.
Series 7 (up to A Town Called Mercy)
SpoilerThe Doctor, the Widow and the Wardrobe(which was actually a present wasn't it?) - Species, Deforestation threatens to wipe out tree spirits
Asylum of the Daleks - Universal*, Insane Daleks escaping would kill even more indiscriminately than Daleks?
Dinosaurs on a Spaceship - Personal, Siluran ark is going to be blown up by missiles
A Town Called Mercy - Local, Gunslinger's siege was killing the town
I'm willing to discuss any of the judgements I have made here.
Oh and something I just realised; series 5 finale is about time never having existed, were as series 6 is all of time happening at once. Nice little reversal there