I mean technically Evangeline could beat them but she's deadly allergic to bee venom, so one sting and she's in danger. There is no antivenin and this world either.
If Eva knew about it, then she could use magic to kill them but she needs to know about them ahead of time.
Since my current story has characters with superpowers, they are capable of dealing with them but their personalities make the outcome vary. It's also an interesting question so I'd like to elaborate on it 
I'll only talk about the main characters' different reactions (I'll add the headshots so the long text doesn't look bleak):
Brick: Would probably hide inside a river or some place until the bees go away. He is powerful enough to kill them (he has sound abilites and could probably just make them explode from the inside or blast them away cause #superpowers) but he is also sensitive to sound (psychological reasons) and would be pretty disturbed by the sound they make, he feels distressed with white noise and the sound bees make would terrify him, so, escaping/hiding is his best course of action unless he needs to protect one of his brothers or something like that. Basically, unless he is forced to, he'd probably just hide. (If he couldn't use his powers for any reason, he'd still look for somewhere to hide and if that's not possible he'd probably get stung by all of them and have bumps all over. He wouldn't die, but he'd be pretty angry at the outcome xD)
Butch: He can make a force field powerful enough to protect himself, so the bees would probably stop chasing him eventually if he can just get far away enough. He can also absorb positivity/life force so he could just kill the bees, but he is aware bees are important and wouldn't want to kill them (he wouldn't admit his reasons to his brothers though). He would kill them if left with no other choice but yeah, he'd rather fly away than deal with them, haha.
If he is unable to use his powers for some reason, he'd try to hide, if there's a body of water he can hide there, he can hold his breath the most between his brothers so he would probably survive the attack XD otherwise he'd be stung and be all like "dammit" but not on the angry side, just annoyed at his useless attempt at escaping.
Boomer: he'd have it easy since he has the ability to talk with insects and he has electricity as his superpower, so, he can just threaten them. I doubt the bees would still attack knowing he can fry them all lol. He could actually manage to convince them to do his bidding and redirect their attacks towards someone else if he feels vindictive enough.
If he couldn't use his powers, he'd probably just let the bees sting him and not really care. As Boomer can't feel pain, he'd be covered with bumps but wouldn't think so much about it.
Barricade: He is terrified of bees, although he has fire powers, he'd probably run away and hide as well unless he is backed into a corner in which he would then burn all of them out of panic.
If he can't use his powers, he is pretty much doomed XD He has a frying pan as his weapon, so, he can't do much with that and being powerless lol, maybe if it was a few but 10,000 is too much lol He'd probably just faint out of fright.
Brazen: He is pretty respectful of nature so he wouldn't want to kill the bees. He absorbs negativity from others and the environment thus he can solve the situation simply by getting rid of their anger.
If he couldn't use his powers he could also get away by holding his breath, but if not able to hide he would get stung and just stay whiny about the experience, being sulky or in a bad mood XD He'd probably use the situation to be pampered and comforted by Barricade (his brother).
However, Brazen is immune to poison so the stings wouldn't make him be in pain or have swelling, he'd just experience the pain from the initial piercing.
Bruise: He would not really care about them being bees and nature being important but he'd probably just freeze them a little and then get as far away as he can.
He'd probably be okay if the bees attack him, his skin is hard to pierce so the bees wouldn't be able to hurt him.
DONNIE: A normal human with only a bat a no special powers. DOOMED!
AJ: A normal human with only a paintbrush, rope, and duct tape. DOOMED!
LIBBY: A flying plush toy who seems to be able to feel pain. Hm... Perhaps if she's quick enough, she may be able to get away unstung. Though, if she is strung, she's probably experienced a LOT more pain then that. So... kinda complicated with her honestly.
THE MASKED STALKEE: Well, SHE lives in a special dream world hosted by Donnie and cannot possibly leave it. So if HE get's stung SHE'D be fine. However...
THAT'S what a bee looks in her world. (Convenient I had this drawn, right?) So... DOOMED!
Generally, the answer seems to be no. My characters would likely NOT be able to go against 10 angry bees.
I got way too into considering this questions, and eventually figured out the answer for each character:
Aviva - Absolutely, yes. Can summon golden fire at will, and if she doesn't shape it it will just go wild. If it's between her and ten thousands bees, it's an instant cremation.
Reyna - She's a normal person with a camera and a shotgun. Kinda screwed.
Vin - Close combat fighter with just about no ranged options. He can throw his gauntlets and pull them back for a long distant punch, but you can't really punch a bee. He might survive but he won't be walking away.
Calcy - Really depends on the location. She's capable of breathing underwater, and bees aren't known for their swimming ability. I know they can submerge temporarily, but they can't really outswim a mermaid. If there's a convenient river, lake or ocean, Calcy takes the dub. Otherwise, kinda screwed.
Matchlock - She's an excellent sniper and capable of delivering nasty kicks, but I doubt either of those will help her. It really depends on how long she can evade them. She's a survivor and mostly nocturnal (part owl, baby), and most bees don't fly at night. If she can last until night, she can escape will they return to the hive. If it's a species of bee that won't give up just because she's gone, or one that flies at night, it'll be harder but I like her odds of getting away.
Veech - He's a doctor. He can fight, but he relies on poisoning his opponent with barbs on his arms and letting them tire themselves out. His species is more closely related to plants than anything, but I really doubt that'll stop ten thousand bees from messing him up.
That's a win, three maybes and two losses. Poor showing from the Cherry Ransom crew.
I have two MCs, and the answers there are... very different.
For Adi... she'd lose. She has no magic, and all of her weapons are mundane. She eventually gets very good at wielding them against much LARGER targets (people, animals, etc), but there's only so much that even a fantastic swordswoman is gonna be able to do against thousands of angry bees.
Koreal.... is a completely different story, however. He's a wizard who is covered with magical tattoos, one of which just makes him totally immune to minor physical damage, and bee stings would definitely fall into that category. Even thousands of bee stings. And he's more than capable of fighting back, because magic. The bees wouldn't have a prayer.
Hey now, a character could be super powerful but just a bad matchup against bees. Saitama from OPM probably can't beat 10.000 bees 
How about 10 and a half (10.500) bees? 
(Now that I think about it, is it a regional thing, using '.' to seperate digits for >3-digit numbers and ',' for decimal points? I remember 6,75 by @igneriss was supposed to mean 'six and three forths' while I'm more used to seeing that as '6.75', just like I'm more used to seeing 'ten thousand' as 10,000 
)
One of Najms abilities is poison tolerence so they'd be ok. however Rahat, Alya and Qamar would probably die, and Qamar and would be super mad about it because they used to hunt giant alien animals but a bunch of tiny insects got them in the end. Rahat and Alya would probably die if there were like 20 bees, they don't go outside much.
Huh, that's an interesting one for sure.
Takara is a vampire, so she's way more resistant to poison, has a higher pain threshold and regenerates. She's also a pretty strong electromancer, so she'll manage to kill the bees... eventually. I assume the personal communicator she carries does not allow her to summon her entire brigade to help, of course, and both her sword and her pistol are pretty much useless against the bees, so zapping them with electricity it is. All 10000 of them. It's going to be a long day...
Amets is also a vampire, but since he's both weaker than Takara and more focused on personal combat, he's kinda screwed. The bees probably won't be able to kill him, though, so it's sort of a draw.
Lt. Janssens and his girlfriend Marja are completely doomed, since they're just ordinary humans. Running away screaming is the best option for them.
Well considering how much Saitama struggled with that mosquito the bees might prove a challenge for him xD
Lyza vs. 10,000 Bees
Lyza is a very capable fighter as she can manipulate sand for attacks and if there are no sources of sand, she can use her physical strengths and the environment around her to her advantage.
Her sand attacks can vary from slicers, punches, shields and on top of that, she also has the Sandstorm attacks. That's a different intensity that she can use which still hasn't displayed to any of her enemies yet because of how devastating those attacks can be. Lyza is extremely crafty and she loves throwing insults to her enemies to throw them off their game.
So, yeah, Lyza can defeat 10,000 bees and she will get hurt along the way especially when she finds a way to put them into one, surround them in a sand power and make a giant ball out of them and goes for a 3-pointer. "You've got BUZZED OUT!!!"
Thank you for the fun question! So here is what Annika has going for her:
Conclusion: Could Annika defeat 10,000 bees on her own? no. Would she get stung at least a few times? possibly. But could she at least run away from the bees? yes. I think the character best suited to defeat the bees would actually be Rose, since she can use flame magic (burning all the bees) and doesn't care about killing bugs.
True. But we can make an exception that those bees are allowed to get killed. xD
@nathanKmcwilliams Rip with the easiest method of getting rid of the bees. (Unga Bunga style
)
@wispysing Vitaly being a pacifist is not a bad thing. 
@sartinjacqueline05 I hope there will be no mix-up with Wasp and the bees; otherwise, Regro has more work on his plate. XD
@AmeTsunami Dude, I think you forgot some zeros. 
@DualDragons @TheLemmaLlama Given that Saitama is a gag character, he can actually defeat 10.000 bees with one punch. 🤷♂️ But it would be funny if he had to struggle the same as with the mosquito. xD
I'm surprised that from all responses I've got, no one, literally no one, even dared to ask, "What's the deeper meaning behind this question?" to me, resorting to answer with, "It's your OC vs. 10.000 frigging bees. The f**k you need a deeper meaning behind this?!"
But I love everyone's take and answers to this question. 
Additionally, I didn't specify the playing field, soooo depends on your imagination where your OC fights the bees.¯_(ツ)_/¯
(Don't you dare change your answer to yes after knowing this. I've got my eyes on you, mister.
)
For example:
Also if he really wanted to, he can ping pong an object like this:
D? He's allergic to bees.... and he isn't very athletic... he'd die... for real this time.
The Season siblings have weather powers so I think they'd win. Also Spring has minor influences over bugs, especially bees.
Mago would probably turn invisible in some hope of escaping them. Not sure how effective that would be though. Maybe even try using her illusions on them too
Mimo would magically construct a box over himself and try to wait it out.
Asa is human so unless she's with Mimo she'd probably lose.
My ocs would most likely kill the bees by using the elemental technique. Frederick would use the power of fire. One giant flame from the palm of their hands and poof! The bees are gone.
Nigel would use the power of water to stun (and possibly kill them).
Kay would do the same as Frederick and use the power of fire.
