You’d die.
Bear eats.
What if instead of swinging the chainsaw you tried to ram it straight into the bear’s face ?
Nobody wins. Any survivor is scarred/crippled for life.
Another example of a ghost of evolution.
Wait, is that supposed to be two categories, or one?
And we haven’t even touched on how a constipated person with a chainsaw would fare.
Has the bear ingested a large amount of cocaine? That might increase degree of difficulty.
I have a pretty big yard with a lot of trees that have an annoying tendency to be blown down during storms or drop huge branches, so I have quite a bit of chainsaw experience. As others have said, bear fur would foul up and jam the blade long before you did any significant damage to the bear.
Chain saws are heavy and difficult to wield, and bears charge with terrifying strength and quickness. I’m thinking that, with one powerful sweep of its paw, it would send you and the chainsaw flying. He would then finish the job with alacrity.
ISWYDT.
The person would die. There’s nothing you could do with a chainsaw that would stop a determined grizzly from killing you. The only question is whether you could inflict a serious wound to the bear that it would later die from.
If you had a hot saw and knew how to use it you might get in a killing blow in before the bear ripped your head off.
Bears gotta eat, same as worms. --apologies to Josey Wales
Will a regular person with a chainsaw kill a charging Grizzly bear? Who wins and dies?
I was in almost the exact same situation a couple years ago!
…alright, instead of a chainsaw, it was a stick…and instead of a bear, it was a mouse. Same idea, though.
The mouse got the best of me that day. But next time, I will be better prepared, with a rigid stick, instead of a bendable twig!
My wife had to know why I was laughing out loud. I told her I’m reading something on the Dope and before I had a chance to explain, she was back to her screen. She’s learned long ago to not ask further questions.
Obviously the person will win. If you think it takes forever to charge your iPhone, imagine the time it takes for a grizzly. Cut the line and you’re all good. Actually doesn’t take a chainsaw to cut a USB cord. Mine seem to be fried if I look at them sideways.
As for the OP, it concerns a “regular person.” Is this in contrast to some sort of trained chainsaw ninja warrior? Do they have them? Do they have silent chainsaws out there somewhere? Can I get my neighbor one for when he’s cutting wood at some godawful early hour on Sunday morning?
If the person is regular at least they’ll be cleaner and better smelling thru the encounter.
Is it a chainsaw that tree-cutters use, that is attached to your belt? If so, climb a nearby tree and saw branches off to drop on the bear and scare it off. After all, everyone knows grizzly bears don’t climb trees, they push them over.
That, or cut down a small tree nearby and use it as a lance in one hand with the saw in the other. Now the bear has two weapons to deal with, will get confused or lose interest, and walk away. 
How long do grizzly bears live? Is it an older bear you can just knock off its charging base, thus interrupting the charging?
I know we covered this in another thread involving knives, put does the person gain an advantage if they pass the chainsaw back and forth between hands?
If you had a lightsaber you would definitely win. Unless the bear had beskar armor.
Are female bears less alacrious? Should one try to determine the sex of the charging bear?
We’re more civilized when it comes to killing and maybe munching on folks.
We should respect their privacy in those matters, though you’re welcome to try. LOL