My ranking of the Big Bads from the in-story perspective of myself as everyman Earth citizen in the Buffyverse:
1. Jasmine - A world where *everything* is theocratic Pleasantville fakeness as long as I worship a vain, megalomaniac goddess with a chance to willingly end up as the next happy meal on legs anyway. I'd rather go to Buffy's isolation tank of bliss which is similar but at least less conscious and without the meal and worship fine print.
2. Glory - All hell dimensions plus their habitats blending into our world merits second place. And Glory was strong and cunning enough that she came very close. It's horror overkill. What's pro-Glory and anti-Jasmine is the fact that death (albeit likely painful and prolonged) is very likely the result in the end of the day in Glory's case as opposed to having permanent face cramps from smiling all the time until the day I die from aging or until I get pleasantly eaten in Jasmine's case. On a day-to-day pre-apocalypse basis, though? I guess I'd be safe because there's no reason given why she'd pursue me in particular. Of course, there's a small chance left I'd end up as brain juice in a 'wrong place, wrong time' scenario. However, it's the end game that really sucks.
3. Wolfram & Hart - Political, economic, social and supernatural power and influence on a global and inter-dimensional scale all the while steadily and purposefully thriving towards a major apocalypse in secured secrecy. And they're lawyers. Rule no.1: no one is safe from them.
4. BtVS S02!Angelus - In thrust the same as with Angel only that his obsession of Buffy was the trigger that made him go all apocalyptic (although, Buffy was a motive in Twilight too). Other than with Angel though, there's also the small chance to end up eaten, tortured or as his new muse and playground for his Artful Human Destruction hobby, though I doubt it. I'm not the innocent damsel type that would make Angelus become all hot and bothered that he'd want to corrupt me. Hee, I'm corrupted enough all on my own.
5. Angel - His dark personality traits, his nature and his doomed circumstances which all intermingle with each other and increasingly bring out the worst, all the while he's sponsored by and under protection of corrupt/evil higher powers (TPTB, W&H, Twilight) make for a *very* dangerous cocktail that can lead an entire city being sentenced to hell just because he wants to make a statement or him buying into the idea that he and Buffy are gods who are destined to create a new world by Nasty Apocalypse and who are entitled to choose who's going to live and die. On the plus side, there's a small chance he saves me from baddies in one of L.A. alleys, which is a mitigating factor that puts him below his soulless self (as long as I don't have to sign away my soul as a result).
6. Adam - I think an army consisting of demon/human/terminator hybrids sounds very dangerous and probably would cost high casualties which could include myself. Still, I fail to see how an army of Adam-like soldiers could hold their own against the superior power in numbers and firepower of Army/Air Force/Navy/Marines combined for too long, even when the US administration doesn't invoke article five of NATO (which I think they would if needed). Adam may be invincible to firearms but I doubt he'd withstand heavy-calibered weapons and nukes.
7. The Master - I just like the creeping evil atmosphere the Master invoked in The Wish. I assume he did roughly the same what he did in Prophecy Girl after he was freed. Running straight on the roof of SHS above the library to do his mojo on the Hellmouth. The fact that the world is still running suggests that he didn't opened it literally. Maybe partially to let pass through some baddies (like the tentacle monster that was about to eat Willow) but the main idea was to unleash its evil energy to slowly sweep over the lands and obfuscating everything. Which is reminiscent to the partially opened Seal of Danthalzar and its effects on some Highschool students in S07 just slower and more indirect in its effects. However, it's not terrifying enough since The Master is weaker than Adam and hardly able to overpower competitors like W&H or to oppose the US military as soon as they get whiff of him or even the Watcher's Council should they finally start to care.
8. Major Wilkins - Yes he would eat many Sunnydale citizens which is bad. However when he reaches Sunnydale's Army base, or just draws enough attention from the public, some rocked launchers and grenades -- maybe a tank or two -- should do the deed. The National Gard should be able to deal with him.
9. The First Evil - In theory, it's the most terrifying Big Bad EVAH! In practice, it's the most stupid and ineffective one. Easily distracted, poor judgement, dubious priorities for an entity that is supposed to be cunning and resourceful and claims ultimate wickedness. Wasting time and effort with Andrew, flirty bickering with Caleb, slicing sex-ay wounds into Spike to name few of its stupid conducts. Acting incredibly stupid and clumsily in failing to open the seal when apparently even pigs blood would do the deed even though it has an army of Bringers at its disposal which it could order to abduct citizens or to break into the zoo or into butcheries. Not killing Buffy when it had the chance(s). Not tormenting Willow, Buffy's most powerful *and* most unstable asset, more and more effectively when it should (tormenting her every night in her bedroom by alternately using Buffy, Tara, Warren and Jenny's shapes to wear her down sounds like a reasonable tactic). Not using Spike's trigger to its advantage even though Buffy outright invited it. Its silly 'I'm so evil and superior that I don't have to be proactive and just wait until you come to me. Muahahaha' conducts. Points for assassinating the Potentials, destroying the Council, breeding an army and the 'hypothetical' threat of doom. Still, something must be wrong with the Turok-Han. Oddly (conveniently), the stronger their number became, the weaker were the individuals. And Wolfram & Hart/Lindsey just needed to send an amulet for its ultimate defeat. Lame.
10. Dark Willow - Minus Giles, I don't fall under her predator-prey system and she's too focused in her procedures. Every attack had a reason and was performed deliberately to specific non-random people and there were no collateral casualties (truck driver, policemen, Rack's customers). If I'd happen to be in close proximity she'd either ignore me or shove me aside. Plus Giles's meddling and minus Xander's Yellow Crayon speech, I'd die. However,the emphasis is on destroying the world, not sending it to hell which would mean serious badness. "She's going to drain the planet's life force, and funnel its energy through Proserpexa's effigy and burn the Earth to a cinder" sounds fancy, quick and willow-y creative. Her motive is ending all suffering out of empathy because the world is a too horrible place to live in....which makes me all the more assume it's supposed to be short and sweet and finite....which kind of takes the edge off it. Still sucks, though.
11. The Trio - They weren't out to kill and harm random folks like me. Maybe my bank account would suffer and their stupidity and recklessness leaves a tiny chance for collateral damage to my detriment.