Game on Saturday, PCs (4 5th & 2 4th, 28 total levels) were hunting goblins in the woods - some failed Survival/tracking checks & a 6 on encounter check later, they were ambushed by 20 goblins & a goblin boss. No PC actually died, but the Wiz did go to 0 hp in the first volley, and it was an incredibly tough fight. Afterwards I checked XGTE encounter building rules and supposedly a moderate/reasonable challenge for a level 5 is 8 goblins, 4 for a 4th... 48 goblins. That would have been a certain TPK.That's just so you can laugh at all the dead PCs.
Edit: And I was going easy on them (and myself) by having the goblins bonus action hide before shooting, not after shooting. Mostly so I didn't have to go over each individual goblin token on Roll20. Also had some suboptimal tactics like a few who charged into melee with squishy-looking PCs.