Update: It's been patched. The drop rate for legendaries in the Widow's Walk lost sector, which players were repeating to power-level their way to Beyond Light's soft-cap, has been nerfed. Bungie tweeted the fix, and millions of voices suddenly cried out in disappointment that they hadn't had time to make use of the exploit, and were silenced.
Due to an issue with the legendary engram drop rate in the Widow's Walk EDZ Lost Sector, we have lowered the rate to its intended frequency.November 12, 2020
Original story: The Beyond Light expansion for Destiny 2 is less than a day old and yet inventive players have already found a way to power-level in record time. Beyond Light comes with a soft cap of power level 1200 which players are already hitting in between 60 and 90 minutes.
As the video above explains, to hit the cap fast you just need to spam a specific lost sector. It's pretty boring (given how much fun new stuff there is to play), but it will make playing the campaign easier because you won't be under-levelled, and it will save you on upgrade modules along the way.
The lost sector in question is called Widow's Walk, and it's located on the left of the Trostland spawn in the EDZ. Once you're there (with a fire team if you really want to go quick) simply kill the boss. In our, ahem, testing, he dropped a legendary every time. For some reason, the gear will be 10 levels higher than you currently are, meaning you can quickly boost up. In order to refresh the lost sector, just run out until you see the word 'Trostland' on the screen, indicating you're in a new area. Rinse and repeat.
Interestingly, you'll also be getting the new ghost mods added in Beyond Light while you're at it, but mostly the point is to hit that soft cap as quickly as you can. There are sections of the campaign where you should be at least level 1160, so getting there now will save some grinding later on.
Of course, like the loot cave and every other Destiny exploit, this one's going to be patched out—maybe even tonight. So while I'm not saying you should abuse this to save yourself some hassle later on, if you're going to then get in quick.