hololive

Source is a little messy:

I originally found it on Pixiv but:
❌low resolution (lower than post), ❌low quality resizing algorithm used, ☑less compressed JPEG, since Pixiv

The artist also put it on Xitter:
☑medium resolution (similar to post), ☑good quality resizing, ❌quite compressed JPEG, since Xitter

The highest quality version seems to be as part of their commission portfolio:
✅high resolution (higher than post), ✅no resizing (original resolution), ☑moderately compressed WebP

Buuuut at full resolution you can actually see some of the flaws in the drawing process, and I also get the impression the artist didn't intend people to pull the full resolution image from their portfolio (as they make a point of saying in their commission ToS that they they reserve the right to post a reduced-resolution version on their socials).