I just now added powdered sugar on accident to my gravey😩

Whatever the cause, the prescription to counteract the sweetness would be to add some acidity. And you might also increase the salt content. Taste your sauce with each addition until you reach the balance you seek.

Did you use corn starch? Is there any chance you mistakenly used powdered sugar instead? I only ask because I've done it! Makes for weird results.

You could add a dash of vinegar -- the acidity should cut the sweetness. I'd use sherry vinegar if you have it.

It might help if you made a roux--equal amounts of flour and either butter or oil, cooked over low heat till well browned, then stir in some chicken broth/stock and add that to your gravy. Also a little red wine perhaps? Does it need salt and pepper? I'm sorry, I'm not sure if I'm helping much, I just can't figure out why it would taste sweet.

It's strange -- I don't know. I didn't add any sugar or the like. I did chop up some of the onions and a couple of carrot slices from the basting pan as they tasted great. Maybe they were somewhat carmelized and that gives it the sweet taste. That's my only guess...

What do you think is giving it a sweet taste?