That is a total mess. Needs a really good scrubbing, and scraping to get rid of all that gunk. The sheetrock on the wall next to the window looks terrible too. No, I definitely would not be happy, and if he made all that mess, he needs to clean it up and fix it.

Amateur work. The drywall could easily be skimmed and sanded. Can’t comment on the wood sill without a picture showing the whole window

Scrap, sand, paint, and I would use an elastic caulking between the window and the drywall return. Compound will always flake out.

Unfortunately this pix isn’t a close-up and we’ve moved however we had a similar metal framed window. Drywall was installed close then PVC trim installed do that condensation would not be an issue.

Pull back and take another photo. Looks like the window stool is completely out of the photo. I can't really tell what is what in this photo.

Is the end of the wall is covering the window jamb. That can't be, can it? Was this existing or newly added?

Very shoddy drywall work and even paint on the jamb??

Is this a real 'contractor'? Or a handyman with substance abuse problems?

All very good questions.
The windows were installed by the contractor. There is no stool. They were installed in our unfinished century home basement (brick).
We hired a contractor to finish the basement and I was shocked to see this is how he “finished” the windows.
All very ridiculous, but here we are. We want to know what we can do to fix this. Do we remove the drywall at the bottom and install a stool?

This is what it looks like from further back

The first thing, I would do, is clean it up. Get all the paint from the walls off the window frame etc. The next thing I would do, is get someone to mud and fix the drywall, because, that looks terrible. By the time, you get all that done, you will have a better idea, of what else you need to do. A reputable contractor, would not have left a mess like that. Maybe look for a new contractor, that actually knows what they are doing.

Looks to me like someone installed a single hung vinyl window on its side to be used as a slider... No good. How long has that been there?

As far as the drywall finishing, that needs to be fixed and cleaned up without question.

" Looks to me like someone installed a single hung vinyl window on its side to be used as a slider... No good. "

Holy s..t, that is a double hung on it's side. You have more issues there than the crappy drywall work. That needs to be torn out asap.

It’s a basement sliding window.

From outside. Weeping holes are at the bottom. It’s a slider

Just realized they are hard to see here (older photo with construction debris) but the weeping holes are there at the bottom of the window.

Looks to me like I see the tile mechanism for a hung window at the very top and very bottom. Maybe I am wrong but............

It’s a single slider tilt window. The contractor who messed up the drywall interior isn’t the one who installed the windows. Windows were directly from the window company.